[Naix]

Originally Posted by Fat Nyara

I'm actually testing Caterpie on a Speed Run on the Yellow Version, it did ok as a Metapod LV7 against Brook, it can just outlast any of the Brook's Pokémon with Harden + Tackle, but it needs Tail Whip support to don't take too many turns, for good call, you have too many options for Leer and Tail Whip than that is not a hard task. Also, in order to any starter to combat Brook's weak point (it's special defense), they need to being solo party, or otherwise you need about 2 hours of gridding to make them ready for the battle, but I'm assuming 3 Pokémon minium, as your starter will have hard times beating all alone (mostly for the PP, and returing to the Pokémon Center for each 2-3 Trainer Battles is not cool).

First of all, I wouldn't consider "outlasting" Brock's Pokemon a good method to beating him in a speedrun. Another thing I'd like to say is that perhaps the most efficient (in terms of experience gain) team size at the time you fight Brock would be 2, as just 1 would be overleveled and (as shown by your playthrough) 3 means you might be having problems with getting your Pokemon up to par for Brock.

Caterpie may seen weak, but it's just as weak as all the Pokémon you have at the moment, and when it evolves to Metapod, it actually have better overall defense than all your unevolved Pokémon, so, it's not really hard to train it to Butterfree.

Even though it might not be too far behind in terms of raw base stats, keep in mind that most Pokemon obtained before fighting Brock know STAB moves either upon capture or within 5 levels of catching them. Also, while Metapod indeed has the highest base Defense of any Pokemon (save for Squirtle) at that time, also keep in mind it has the lowest base Attack, which when combined with its lack of STAB means it's hitting for squat.

Mankey and Spearow are really great at the early point, too, Mankey can't man-handle Brook with Low Kick (Geodude and Onix usually beat him 1vs1), but with the enough support from it's friends, he can do the job done, but he needs too many experience to learn Low Kick for my like.

Keep in mind that Mankey needs less experience to learn Low Kick (learned at level 9) than Butterfree to learn Confusion (level 10) or Nidoran to learn Double Kick (level 12), making it the best option for dealing with Brock regardless. Also, it's not like Mankey can't fend for itself until then, as its lack of STAB is mitigated somewhat by the highest Attack stat of any Pokemon obtained prior to Brock (Something to remember is that Mankey can be caught at level 5, which means it only needs 4 levels to learn Low Kick). Another thing I don't get is "Mankey can't man-handle Brook with Low Kick". Why wouldn't it? In addition to great Attack (at least at the time), it also has STAB on an attack that hits both of Brock's Pokemon super effectively.