Ryan and Bryan always battle together in Tag Battles with their Quilava and Croconaw, respectively. Ash and Dawn heard how powerful they were and challenged them using Turtwig and Piplup, respectively. Fortunately for them, Turtwig and Piplup had a hard time working together, as did Ash and Dawn. As a result, the twins won the battle easily.
Proud of their victory, Ryan and Bryan went to look for other Trainers to beat until they found a table with a pile of fruit on it. However, it was a trap set up by Team Rocket in order to steal their Pokémon. When Ash and Dawn came back for a rematch, they told them what happened. It was then that Turtwig and Piplup showed real teamwork and saved Quilava and Croconaw. As thanks, Ryan and Bryan took up the offer of the rematch, but they ended up losing this time around.
This listing is of Ryan and Bryan's known Pokémon in the anime:
Ryan used Quilava with Bryan's Croconaw to defeat Trainers and earn their winning streak of sixteen. For their seventeenth win in a row, the twins battled Ash's Turtwig and Dawn's Piplup. However, due to the two and their Trainers arguing, the twins eventually won. Quilava was stolen by Team Rocket with Croconaw, and they were rescued with the help of Ash and Dawn, who now got along better. After that, the twins battled them again. However, they lost to the two's teamwork.
Bryan used Croconaw in Tag Battles with Ryan's Quilava. After their sixteenth victory, the twins battled Ash and Dawn, whose Turtwig and Piplup were defeated due to disagreements. Later on, Croconaw was stolen with Quilava and Ash and Dawn, now feeling better about each other, were able to rescue the two. The twins then had a battle with them; however, they were defeated, ending their winning streak at seventeen.