Here I will post info on the Pokémon that join Ash & his friends during their travels through the Sinnoh Region.

Ash's Team


Pikachu
Pikachu was Ash's Starter Pokémon. It started off disobedient to Ash but soon changed its ways after seeing Ash defend it against a flock of Spearows. Since then Pikachu alone has assisted and been the cause of many of Ash's wins in battle and over time has adopted Ash's mannerisms. Pikachu hates being in its Pokéball so always stays out.


Staraptor
Ash's Staraptor evolved from Staravia during a PokéRinger contest against Paul's Honchkrow. As it has evolved, it is likely to become one of the powerhouses of Ash's team and will still likely be used for long-distance searching. With it's bigger size and strength, as soon as it evolved, it learned the move Close Combat, which will be helpful for many close flying battles.


Torterra
Torterra is the Grass type Pokémon of Ash's Team. After being used in a gym battle against Volkner, which got postponed, Ash's Grotle evolved during a battle with Team Rocket. With its new size and strengths, it now knows more powerful moves such as Leaf Storm in addition to the moves Energy Ball, Rock Climb & Synthesis. With these attacks at its disposal, it is sure to be a massive tank in Ash's team.


Infernape
After being knocked to the brink of fainting in a battle against Barry's Empoleon, Monferno went berserk with its Blaze Ability and unleashed its full power against Team Rocket. While protecting the Pokémon, it evolved into Infernape. Infernape has many powerful attacks at its disposal such as Flame Wheel so it's set to be the powerhouse behind Ash's team. It was later used in a battle against Flint's Infernape, but lost due to its lack of experience.


Buizel
Originally captured by Dawn, Buizel has always been an incredibly strong Pokémon with an aptitude for Pokémon Battles. After Zoey saw how Ash & Dawn had Pokémon that preferred the other's vocations, a trade followed. Now, Buizel is one of Ash's powerhouses with powerful moves such as Aqua Jet at is disposal, it will likely be called upon often for battles.


Gliscor
During its Gligar stage, Gliscor was a fairly weak Pokémon, not knowing many attacks and thus not being very strong, all due to its age. However, evolving by grabbing a Razor Fang while it was falling, it has gained a lot of strength and confidence. Even after evolving though, it still wishes to battle more and still vies for Ash's approval. With powerful attacks such as Steel Wing and X-Scissor, it is sure to become a vital member of Ash's team. During a battle with the Air Battle Master, it learned Giga Impact but decided to stay for training.


Gible
Ash first encountered his Gible when he met Old Lady Tatsu, a woman who teaches Dragon Pokémon the special move Draco Meteor. Ash assisted Gible in the learning of the move and Gible decided to follow Ash. It also has the habit of biting on to heads. Later on, Ash noticed Gible followed him and eventually captured it. It has many powerful attacks such as Draco Meteor, Dig and Dragon Pulse and is sure to be a powerhouse of Ash's team.


This is my 18600th post!!!!!!

Brock's Team


Sudowoodo
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
Croagunk is a rather stubborn Pokémon. Meeting him at an unofficial Pokémon Gym ran by Team Rocket, Brock & 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 & poison attacks and will become a vital asset to Brock's team

Happiny
While on the boat to Twinleaf Town, Brock's Happiny evolved into Chansey while trying help a Pichu to . 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.

Dawn's Team


Piplup
Having run off from the lab in a dispute with Chimchar, Dawn finds Piplup trapped in a web and helps it out. Piplup & Dawn grew a close bond very quickly. Piplup can be described as a brat, but it truely tries its best in battles, despite the fact that its not the most powerful Pokémon. Dawn tends to let Piplup stay out of its Pokéball but does keep it in sometimes.

Buneary
After having various Buneary attack her during her travels, Dawn came across another Buneary. Eager to add it to her team, she attempts to battle it and eventually succeeds and captures it. Buneary is female and appears to have a crush on Ash's Pikachu and knows many poweful attacks including Ice Beam.

Pachirisu
During her travels, Dawn met up with a hyper Pachirisu. After several problems between Pachirisu and the group, Dawn eventually befriended the cute little squirrel. It is a loving Pokémon, that is known to shock Dawn whenever it is happy, causing Dawn a Bad Hair Day. However, it has some powerful attacks including Spark so it is able to hold its own in battle.


Mamoswine
After evolving from Piloswine, Mamoswine seems to be even more hot-headed and immediately charged at Ash & Co.. With its powerful attacks such as AncientPower and Ice Shard, Mamoswine is the major massive powerhouse of Dawn's team. After it evolved, it had trouble obeying Dawn until Dawn managed to convince it to obey when she took care of it when it was injured. When it's not in battle, it has a habit of sleeping.


Cyndaquil
After receiving the egg from Kotone in the Johto Festival, the egg quickly hatches into a Cyndaquil. Cyndaquil is clingy of Dawn and was constantly fighting with Piplup for her attention. It has some powerful attacks at its disposal including Flame Wheel, Swift and Smokescreen which will sure help it become a vital part of Dawn's team.


Togekiss
After allowing a princess called Salvia to take her place in a Pokémon Contest, Salvia was kind enough to allow Dawn to have her Togekiss so that Togekiss can partake in Pokémon Contests, which Salvia herself is unable to do. Togekiss has many powerful attacks such as Aura Sphere that allow it to be able to be able to hold its own in battles as well as create dazzling appeals.

What happend to ash's original pokemon ?

If you visited various fansites, like this one, you'd know what happened to them.


Edited the Pokémon info since Ash & Dawn both got new Pokémon and some evolved.