Having evolved from Bonsly, Sudowoodo has shed it's child like persona and has become a powerful Pokémon of Brock's team. With Powerful attacks including Mimic and Headbutt, Sudowoodo is the powerhouse of Brock's team.
Croagunk is a rather stubborn Pokémon. Meeting him at an unofficial Pokémon Gym ran by Team Rocket, Brock and Croagunk quickly gained a close friendship. Eventually teaming up together to get rid of Team Rocket, Croagunk decided to join Brock's team. It has many powerful fighting and poison attacks and will become a vital asset to Brock's team. When Brock sees a girl, Croagunk uses Poison Jab on him.
While on the boat to Twinleaf Town, Brock's Happiny evolved into Chansey while trying to help a Pichu. It is currently unknown if Chansey has kept the strength it had as a Happiny, but it knows the move Softboiled which it used to heal the Pokémon on the boat.
Brock has only met his recently evolved Steelix once. Evolving while under the control of his brother Forest, it remains loyal to Brock and follows his commands at will. It has gained strength after the evolution and remains to be an amazing Pokémon at the Pewter Gym for Brock to call upon whenever he needs it. Brock's Steelix debuted in Showdown In Pewter City as an Onix and in Grading Spaces as a Steelix.
How Brock obtained Geodude is unknown, however Geodude has always been a vital member of Brock's team, always being there for battle or for certain contests. Geodude is an unfailingly fun loving Pokémon that is known to have fun with Pikachu and the other Pokémon on many occasions, however it was seldom seen. When Brock left for Hoenn, he also left Geodude in Forest's care. Brock's Geodude debuted inShowdown In Pewter City.
Evolving due to Brock's immense care and bond with it while in battle with Team Rocket, Crobat is a Pokémon that follows the orders of its trainer. With its four wings, it is a super fast flying Pokémon that has been known to help Brock out of jams on several occasions. When Brock left Pewter Gym for Hoenn, he left Crobat under the possession of his brother Forrest, however Crobat is overjoyed to see Brock whenever he returns to the gym. Brock's Crobat debuted in Clefairy and the Moon Stone as a Zubat, 'Hassle in the Castle as a Golbat and Control Freak as a Crobat.
After evolving from Pineco, Forretress became Brock's most commonly used Pokémon. It got over its habit of exploding when near Brock and became a powerhouse. Forretress was the only one of Brock's Pokémon that he took to Hoenn with him and resided as a vital member of his team until Sinnoh. Brock's Forretress debuted in Entei at Your Own Risk as a Forretress.
After evolving, Marshtomp became a strong Pokémon often used to settle feuds or just in simple battle. Marshtomp is a well mannered Pokémon which takes after it's trainer a little bit in regards to romance. Brock notably used Marshtomp in a Pokémon Contest against May. Brock's Marshtomp debuted in A Chip Off the Old Brock.
After finding a Water Stone and evolving, Ludicolo became a more friendly and energetic Pokémon and is known to dance on occasion. It has not been used in battle often so it's true battling power is still unknown. When Brock returned home from Hoenn, he decided to leave Ludicolo at the gym to entertain his family.
Vulpix was an incredibly particular Pokémon, only eating food that either it's original trainer, Suzy, or Brock made. Through seeing the care that Brock went into in looking after Pokémon, she decided to let Brock look after it. Brock was often seen grooming it and sometimes used it in battle, mostly however in training with Ash. Vulpix, while a little spoiled, did enjoy playing about with the other Pokémon. Eventually Brock met up with Suzy again and decided that Suzy should keep Vulpix again.