Hoothoot is available in the following locations at night: Routes 1, 2, 5 (Crystal only), 25 (Crystal only), 29, 30, 31, 35, 36, and 37, National Park. Hoothoot is also available during the day in the following locations: Routes 26, 27, 32 (Crystal only), 34 (Crystal only), 35, 36, 37, 38, 39, Azalea Town, Ilex Forest, National Park, Lake of Rage (Headbutt trees). Noctowl is available in the following locations at night: Routes 2, 5 (Crystal only), 8, 11 (Crystal only), 13, 14, 15 (Crystal only), 25-27 (Crystal only), 37-39 (Crystal only) and 43.
Out of the three early-game Normal/Flying types, Hoothoot is a freaking tank. Whereas Pidgey and Spearow have solid Attack and Speed, Hoothoot has decent HP and Special Defense. The only problem is that even if it can do a better job at tanking hits, it's not going to be doing nearly as much damage in return (or WITH Return, for that matter). Although using a defensive Pokémon is in general worse than using an offensive one (simply due to critical hits), Hoothoot is nonetheless the best defensive Flying-type you can use apart from legendaries. For one, our little owl gets access to the indispensable HM Fly, which immediate makes it infinitely better than Ledian and Butterfree. More importantly, Hoothoot gets access to two amazingly good support moves in Hyponsis and Reflect. Both these moves, in tandem with its great overall bulk, give Hoothoot a somewhat better chance to win against various boss battles than its cousins Pidgey and Spearow. Just so long as you don't recklessly switch Hoothoot in expecting to tank everything that anything throws at it, you have yourself a very decent support Flying-type.
Gym #1 - Falkner (Violet City, Flying-type): The Pidgey shouldn't be too much trouble, but against the Pidgeotto, all you can really do at this point is spam Growl and switch to a teammate which can do decent damage.
Gym #2 - Bugsy (Azalea Town, Bug-type): You absolutely have to be at least level 16 by this point so that you can use Hypnosis on the Scyther. If it hits, you have a good chance of winning, but if it misses... well, you better hope Scyther doesn't get a Fury Cutter streak going.
Rival (Azalea Town): Hoothoot can actually solo this fight pretty easily if you picked Totodile. Just want out for Gastly's Curse.
Gym #3 - Whitney (Goldenrod City, Normal-type): Your best bet is to use Hyponsis first turn and hope you get lucky; just know that even a max attack Return from Noctowl is barely going to dent Miltank.
Rival (Burned Tower): You can solo this fight except for the Magnemite.
Gym #4 - Morty (Ecruteak City, Ghost-type): Noctowl's typing and bulk allow it to matchup very well against this gym. However, you will almost certainly have to switch out at least once due to the ghost mons' tendency to use Curse. Also, be wary of using Mud Slap, as that move can easily be Spited down to zero PP. Against the Gengar, it all boils down to whose Hypnosis will hit or miss. Definitely equip a Mint Berry if you have one. Worst-case scenario, Noctowl SHOULD be able to tank a Dream Eater without too many problems, but you really don't want to let it come down to that.
Eusine (Cianwood City, Crystal only): You can easily beat his Drowzee and Haunter, but you do not want to have to tank a STAB Thunder from Electrode.
Gym #5 - Chuck (Cianwood City, Fighting-type): You can try setting up a Reflect, but you're just begging Primeape's Karate Chop to crit. The Poliwrath matchup is similar to the Gengar matchup: whose Hyponsis will hit? If you manage to PP stall its Dynamicpunches, you can win easily, but be very careful about crits and confusion hax and Hypnosis misses. They WILL happen.
Gym #6 - Jasmine (Olivine City, Steel-type): You can theoretically Hyponsis the Steelix, set off a Reflect, and then switch to a strong offensive mon, but why not just use that strong offensive mon in the first place?
Rocket Executive battle #1 (Team Rocket HQ): Unfortunately, even a max happiness Return will most likely not OHKO the Koffing here, who will then Selfdestruct you to doom. Similarly, the Raticate will probably outspeed and deal a lot of damage with Hyper Fang. Tread lightly unless it's Zubat.
Rocket Executive battle #2 (Team Rocket HQ): A much easier fight. The Pokémon this Executive has don't have strong moves; Murkrow has Pursuit though, so be sure to not switch out in low health. Have Fly or Return handy and you'll win.
Gym #7 - Pryce (Mahogany Town, Ice-type): Provided you are in the mid-30s by this point, Noctowl definitely won't get OHKO'd by any non-crit move Pryce can throw at you. This gives you an opportunity to use Hyponsis at will and switch to a powerful offensive mon. But again, similar to Jasmine, why not just use that powerful offensive mon in the first place?
Rocket Executive battle #3 (Goldenrod Radio Tower): Everything has Selfdestruct. Noctowl is a good tank, but Defense isn't its speciality. Use something else if you can.
Rival (Goldenrod Underground): His lead, Golbat, can be tricky with Confuse Ray + Wing Attack. Haunter can't touch you at all with the exception of Curse, which is always annoying. You can actually beat the Magnemite without too much trouble as long as you have Mud Slap. The Sneasel is easy since it doesn't have any Ice-type attacks (although even if it did, you'd still be alright). Any three of the rival's starter mons will be very easy to handle, too.
Rocket Executive battle #4 (Goldenrod Radio Tower): This is pretty much the same situation as the Team Rocket HQ. Just repeat what you did there: mostly spam Fly or Return, heal if necessary.
Rocket Executive battle #5 (Goldenrod Radio Tower): Noctowl matches up very well with Admin's Houndoom. Noctowl should be able to avoid the 2HKO just fine and alternate between Hyponsis and Return when needed. Houndour and Koffing are easier, especially since this Koffing lacks Selfdestruct.
Gym #8 - Clair (Blackthorn City, Dragon-type): Again, this is a situation in which Noctowl benefits from its special bulk. The first Dragonair is easy, but being Thunder Waved can be pretty annoying. The other two Dragonairs have Thunderbolt and Ice Beam, respectively, so you probably want to avoid those matchups. The Kingdra, however, isn't all that bad as long as you're not afraid to use a Hyper Potion whenever necessary. Just be wary that she probably will use Hyper Beam once you're in KO range. SmokeScreen is always annoying, but you can give her a taste of her own medicine with Mud Slap and Hypnosis.
Rival (Victory Road): Similar situation to the one before. Sneasel (his new lead) is super easy, as always. Golbat and Haunter are still annoying but beatable. The Magnemite has evolved, so stay away from that. Silver happened to take a page out of Blue's playbook and added a Kadabra, which Noctowl can easily feast on barring major Confusion hax from Psybeam. Finally, all three of the start mons can still be handled somewhat well by Noctowl, although poison and accuracy losses from Meganium's PoisonPowder and Typhlosion's SmokeScreen are never fun.
Elite Four Will (Indigo Plateau, Psychic-type): You can probably avoid the 2HKO from the Xatus' Psychics barring hax, but the only significant damage you can do is max happiness Return. The Eggecutor you can handle just fine. The Slowbro is tanky as heck, so all you can do is Hyponsis it. The Jynx has Ice Punch, so avoid that matchup.
Elite Four Koga (Indigo Plateau, Poison-type): Noctowl's main purpose during this fight will be to use Hyposis and get the heck out. The only exception is against his lead, Ariados, which you should be able to kill with Fly. However, even this is pretty risky, as you give Ariados ample opportunity to set up Double Team + Spider Web + Baton Pass and then before you know it, you have a dead owl. (In this gen, Baton Pass "passes" Spider Web's trapping ability in addition to the Evasion boosts.)
Elite Four Bruno (Indigo Plateau, Fighting-type): If you try to use Fly against Hitmontop, it will just use Detect, so this matchup will take an eternity for you to win. Similar situation with the Onix. Hitmonchan is really easy if you just spam Fly. Lee is a little more difficult due to Hi Jump Kick (albeit thankfully only an 85 BP move this gen) and Swagger, which WILL cause you to hit yourself in confusion.
Elite Four Karen (Indigo Plateau, Dark-type): Umbreon is immensely bulky, so really the only thing you can do is Hyponsis it and swtich to a strong offensive mon. The Vileplume and Murkrow are easy. Gengar can be dealt with, but please, watch out for Destiny Bond. You can handle her Houndoom similarly to how you handled that Rocket Admin's Houndoom: put it to sleep, spam Return, and Hyper Potion up when necessary. Rinse, repeat.
Champion Lance (Indigo Plateau, Flying-type): First off all, every single one of his mons has Hyper Beam, which will do a significant amount of damage to our owl if not KO it outright. Thankfully, the AI pretty much never uses Hyper Beam first turn, giving you an opportunity to set up a Reflect and then use Hyponsis. Just be wary that all six of Lance's mons are pretty dang bulky, so Return won't do jack to any of them except for perhaps the Gyarados and Charizard.
From this point onwards, you can fight the gyms in any order, though you will need to retrieve the Machine Parts from the Cerulean City gym before you have access to the earlier portion of Kanto. Feel free to anticipate or postpone any battles as needed.
Gym #9 - Brock (Pewter City, Rock-type): Noctowl is entirely inadequate in this fight. Don't even attempt to put Brock's Pokémon to sleep, the low accuracy and their Rock moves are just not worth it. Let something else take them on instead.
Rival (Mt. Moon, optional): Alakazam is stronger than Kadabra and Gengar has replaced Haunter, but other than that, that's pretty much it. Noctowl, much like in Victory Road, only really needs to avoid Magneton, and while it may struggle against the starters, it can pull off a victory in a pinch.
Gym #10 - Misty (Cerulean City, Water-type): The main threats here for Noctowl's health are Lapras and Starmie, which have Ice coverage. Lapras is the most dangerous, due to STAB. However, Noctowl's bulk allows it to take Starmie's hits. If you manage to use Hypnosis on Misty's team, you can whittle down their health just fine.
Gym #11 - Lt. Surge (Vermilion City, Electric-type): Noctowl may theoretically win this, due to the obvious level advantage, but it's still not wise to put a Flying-type with low Defense in an Electric gym where there are Pokémon that can explode. Use it only if you are entirely out of options.
Gym #12 - Erika (Celadon City, Grass-type): Fly does well here. It helps that Erika's Pokémon are not particularly offensive-oriented, except Victreebel, but its strongest move is Acid. Noctowl will be fine.
Gym #13 - Janine (Fuchsia City, Poison-type): The low level of these Pokémon makes them easy to fight. Maybe use something else against the two Weezing, which can explode, but it's a safety measure you probably don't need. Noctowl can use its typical Hypnosis tricks here, and then whittle them down with Return.
Gym #14 - Sabrina (Saffron City, Psychic-type): Noctowl's bulk makes it absorb the nasty Psychics fantastically from all of these Pokémon, and Return will eventually take them down. Make sure you put them to sleep first, though; Psychic can lower Special Defense and eventually make the fight troublesome even for the owl.
Gym #15 - Blaine (Seafoam Islands, Fire-type): Avoid Magcargo. Its Attack is low, but Noctowl can't do much of anything to it. Likewise, Magmar has ThunderPunch. Rapidash is the least dangerous, and can be defeated with the usual technique.
Gym #16 - Blue (Viridian City): Pidgeot can wrestle with Noctowl, and Noctowl will probably win unless Hypnosis misses and Pidgeot resorts to Mirror Move. Arcanine and Gyarados, however, both have strong physical attacks that Noctowl should be wary of, even with Reflect as they can score critical hits, and Rhydon is absolutely frightening and not for Noctowl to fight. Exeggutor and Alakazam are safe, as Noctowl can absorb their hits well.
Rival (Indigo Plateau, optional): Crobat has evolved and become more annoying than before, but not much stronger. It will be more difficult to defeat, but that's it. Everything else works exactly as it did in the previous matchups.
Red (Mt. Silver): You win against Venusaur and MAYBE Espeon, but that's it. Charizard and Blastoise are stronger than Noctowl and can be Hypnotized at best, whereas Pikachu and Snorlax pack a punch and should be avoided altogether.
In case you glossed over the "important matchups" segment, both Hyponsis and Reflect are extremely valuable. Hoothoot learns Hyponsis at level 16 and Noctowl learns Reflect at level 25. Not only is Hyponsis awesome against basically every single boss fight, but it is an indespensable tool for catching wild Pokémon in a region where most of the time you'll be trying to catch much lower-leveled mons. Hypnosis' usefulness cannot be overstated. Unfortunately, Hoothoot's notable level-up movepool ends there.
For TMs, however, it has some good options. Fly is by far the most important move Noctowl can learn, as it guarantees safe travel. Swift is a great early-game move that allows Hoothoot to actually deal significant damage to stuff. The same is true for Return with Noctowl's late-game success. Of all three early-game Normal/Flying types in Johto, Hoothoot makes the best use of Mud Slap, as it can actually tank a hit or two from strong Pokémon who happen to push through the accuracy drop. Swagger and Attract may be decent options if you want your Hoothoot to be more stally, but they are inadvisable since if you have a free turn to use a support move, you might as well just use Hyponsis.
There are two moves not mentioned that theoretically mesh really well with Hyponsis, but are very bad for different reasons: Dream Eater and Nightmare. Dream Eater would be a great move on Noctowl, but its learnt WAY too late, at level 57, and the TM for it isn't until Kanto. The TM Nightmare, by contrast, can actually be obtained before the third badge, but its mechanics are terrible. You basically have to use Nightmare during each individual sleep cycle, even if the opponent does not switch out, so basically you would have to use Nightmare over and over again every single time you put a mon to sleep. If you still want to use Nightmare even after this explanation, then by all means go for it; just be ready to waste a whole bunch of time.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Hoothoot Line Ratings
At what point in the game should I be evolved? You absolutely want to have a Noctowl by the time you face Whitney. She's just too good.
How good is the Hoothoot line in a Nuzlocke? Hoothoot is a wall, which is pretty rare for both a Normal and a Flying-type. It has accesst to Fly, Hyponsis and Reflect, all of which are amazing support moves in their own way. The defensive utility that Hoothoot brings to the table is completely nonexistent in Pidgey or Spearow. Granted, its offensive presence leaves a lot to be desired (Noctowl's Attack is even lower than that of Spearow), but who cares about offense when you can slowly sleep your opponents to death?