Brock is the leader of Pewter City gym in Gen 1 (Pokemon Red) , Gen 2 (Pokemon Crystal) , Generation 3.5 (Randomized FireRed) , Gen 4.5 (Randomized HeartGold) and Anniversary Red . He serves at the first gym leader faced in the Kanto region generation games.
It is believed that he follows the Old Amber, as his stronger teams contain both Omastar and Kabutops, and in the Anniversary run this also included Aerodactyl, completing the trio of Fossil Pokémon, while his rematch team included all three.
Teams [ ]
Original Red [ ]
Versus Brock
Level
Pokemon Name
Type
Moves
12
Geodude
Rock/Ground
Tackle, Defense Curl
14
Onix
Rock/Ground
Tackle, Screech, Bide, Bind
Crystal [ ]
Versus Brock
Level
Pokemon Name
Type
Moves
41
Graveler
Rock/Ground
Defense Curl, Rock Slide, Rollout, Earthquake
41
Rhyhorn
Ground/Rock
Fury Attack, Scary Face, Earthquake, Horn Drill
42
Omastar
Rock/Water
Bite, Surf, Protect, Spike Cannon
42
Kabutops
Rock/Water
Slash, Surf, Endure, Giga Drain
44
Onix
Rock/Ground
Bind, Rock Slide, Bide, Sandstorm
Randomized Fire Red [ ]
Versus Brock
Level
Pokemon Name
Type
Moves
12
Venonat
Bug/Poison
Poisonpowder, Megahorn†
14
Ledian
Bug/Flying
Megahorn†
Randomized Heart Gold [ ]
Versus Brock
Level
Pokemon Name
Type
Moves
51
Sealeo
Ice/Water
???†
51
Delibird
Ice/Flying
???†
53
Glalie
Ice
???†
52
Mamoswine
Ice/Ground
???†
54
Sealeo
Ice/Water
???†
Anniversary Red [ ]
Versus Brock
Level
Pokemon Name
Type
Moves
15
Onix
Rock/Ground
Bind, Screech, Tackle
17
Aerodactyl
Rock/Flying
Rock Slide, Wing Attack, Agility
Rematch [ ]
Versus Brock
Level
Pokemon Name
Type
Move
100
Onix
Rock/Ground
TBA
100
Rhydon
Ground/Rock
TBA
100
Golem
Rock/Ground
TBA
100
Omastar
Rock/Water
TBA
100
Kabutops
Rock/Water
TBA
100
Aerodactyl
Rock/Flying
TBA
† If anyone has the move data for these pokèmon, your help would be appreciated.