Fun fact for the one person on the planet that doesn't already know this: while Kakuna only knows Harden if caught in the wild (strangely at Level 5...), if you evolve it from a Weedle, it retains both Poison Sting and String Shot, making it...well, a little easier to level without just having them first in the party and swapping out, which you will probably still have to do a lot. Attack power is useless, as is their Speed, but they're able to take hits, and they're good for stalling and trying to poison the opponent before swapping Kakuna for something that hits like it actually has balls. But in any case, a Kakuna that can actually DO SOMETHING other than Harden spam. Same thing applies with other worm Pokémon that turn into cocoons, like Caterpie and Wurmple.

The more you (probably already) know!