Stephan is a recurring character and rival and friend of Ash Ketchum.
Stephan first appeared in Oshawott's Lost Scalchop! where he challenged Ash into a battle and sent out his Blitzle as his Pokemon. Ash was originally going to battle him with Pikachu but Oshawott offered himself to battle. The battle was postponed after Oshawott's scalchop was sent flying. Cilan then asked him if he could wait the next day until and have another battle with Ash, he agrees and then says he is going to train his pokemon in the mountains and to come and find him in the mountain. The next he was seen training his Blitzle by powering up his electricity using his bike powered generator, Ash the challenged him into a battle where he lost and was really impressed that Oshawott beat his Blitzle even though he had a type disadvantage, he then shook hands with Ash and said they were going to battle again.
He later reappeared in Reunion Battles In Nimbasa! during the Don Battle Tournament. Where he met up with Ash and his friends riding on his newly evolved Zebstrika and reveal he was going to enter. In the next episode, he went agaisnt Bianca in the first round of the tournament. He used his his Zebstika agaisnt Bianca's Minccino and managed to defeat it.
He appeared again in Climbing the Tower of Success! to compete in the Bell of Wishes Festival Contest and won. He accompanied Ash and co. to the next town for the Donamite Battle Competition. Stephan won the tournament after beating Montgomery and his Throh.
He made an appearance in BW043 and battled Iris' Emolga at the quarter-finals of the Don Battle Tournament. During the battle Sawk showed the extent of his power by stopping Emolga's Attract with Close Combat. However, Emolga's Static paralyzed him resulting in her victory. It reappeared in BW071 and, like Stephan in the cosplay contest, it dressed up as Nurse Joy's Audino, and was his ace in the Clubsplosion and Unova League.
Stephan seems to be a sort of replacement to Team Rocket's Butch. This is due to the fact that no one pronounces either names right. But starting from BW105 the gag was retired as Ash and his friend started to pronuonce his name right, much to his pleasure.
In "Climbing the Tower of Success," Iris pronounces his name right after the barrel race.
Stephan has been defeated by Ash two times and has never even won against him.