How did you make it past the first gym in yellow?

[TicoPokemonMaster]

haha, I use to hate Geodude and Onix when I had to face them but after I would catch and train them.

When I was young I would emulate Ash's team by brock's gym I would have pikachu, butterfree, pidgeotto(lv7), and nidoran( I know it wasn't Ash's but I wanted something different, it would usually replace butterfree's place after I was bored with it.)

With butterfree I would spam Confusion and win

[GengarsRevenge]

Yeah, evolved Caterpie into Butterfree so it could learn confusion. Then it became easy.

For some reason I didn't like Nidoran, so I didn't bother training one...

[MugoUrth]

I pretty much did it the hard way. I keep leveling up my mon until I am able to beat him. But like everyone else said, if you don't want to do it the hard way, get a pokemon with a good fighting move.

[Antiyonder]

I'd pretty much just use Butterfree's Confusion and Mankey's Low Kick do the job.

Though at one point I played through Stadium to get the Surfing Pikachu (With Mew and Mewtwo as my main fighters since Pikachu would be at a low level), and used Surf attack on Brock's Pokemon.

[Noheart]

I aimed for the horn.

Oh and Butterfree.

[darkfalcon922]

nidorina>geodude and onix

[Corinton]

A level 13 Pidgey and I won the battle easily thanks to gust xD

[Mudkipz_Lover]

I just used status lowering from Pikachu, Pidgey's gust and I used Nidoran (don't remember is M or F) to waste my time to heal my Pokémon.

[Deicario]

Well, everytime I lost I'd go and face him again.
I can't remember my tram but it'd probably be easy ones to get like Pidgey (plus Pikachu
of course).
Eventually, I beat him. But I had very small amount of money left.

[sAv1Or)]

Butterfree + Confusion or Nidoran + Double Kick

[Skwog]

Either Nidoran with Double Kick or Butterfree with Confusion. I remember my first time trying to beat Brock with only Pikachu...

[hawaiian ale]

i caught a nidoran. had it evolve to a nidorina so it learned doulbe kick.

[QingLong]

A Mankey
Enough said

[The Tail]

I caught a Mankey and a Nidoran. Also Tail Whip'd the Onix 'til his defense couldn't be lowered (had a high leveled Pikachu that wistood its attacks) juust in case.

[Grannel]

Used Butterfree and spamed confusion.

[Victoria]

Darling, electric is not in any way weak to rock. It was Onix and Geodudes second type, Ground, which rendered Pikachus electric attacks useless. But as pretty much everyone else, I used Butterfree/Mankey to get the badge.

[childxofxthexgrave]

I used the popular Mankey Low Kick method, with a little help from Butterfree's Confusion.

[Adrexus]

Training Pikachu to level 20 so I could defeat Brock with slam. That gym took me so long to beat. But it was worth it.

[ExeDivinus]

I forced my way into victory!
I caught a Pidgey first then a Caterpie, evolved it into Butterfree.
I did it like this first my Lv. 10 Pidgey used Sand Attack up to six stages then switch in with Pikachu Lv. 20 and use Slam over and over Butterfree was for backup in case Slam ran out. When I was fighting Geodude I scored 3 critical hits and two for Onix.
Sand Attack was to prevent them from hurting my team.

[Sprintking]

Mankey with low kick, or alternatively, Nidoran with double kick. I prefer the second option because Nidoking is a E4 viable pokemon.

[caterpie2]

Nidoran with double kick... Brock didn't stand a chance.

[ZeroTrouble]

Easy, Mankey + Butterfree = WIN

[MonsieurKuitaran]

The commonly stated Nidoran Male + Double Kick combo.

[Saga]

Out of all 1st Generation games, Yellow is the easiest to begin with. Getting past Brock has SO many options... get a Mankey, train a Nidoran until it learns Double Kick, or get a Butterfree and raise to level 12 when it learns Confusion. Even Pikachu himself can do it because it can learn Double Team at level 15, so it can dodge any attack, while patiently wearing Geodude and Onix down (which have inaccurate attacks to begin with).

Pokémon Blue is the next easiest. No Mankey, and Nidoran don't learn Double Kick until they're high enough to take on the Elite Four. So, Butterfree, is the best bet (other than your Starter, of course) - which in this version learns Confusion immediately after evolution, and is easily found on Viridian Forest.

Red version, however, is a bit of a pain if you took Charmander... you also only have Butterfree to rely on, but finding a Caterpie is hard work. While there's a 50% chance (85% if you count Metapods too) to find one in Blue, in Red there's only 5% (10% with Metapods).

[SoulSilverMstr411]

Even at level 10 Butterfree's Confusion pwns Brock's pokemon. The battle lasted maybe 30 seconds.