So, I was listening to Minna de Arukou (the Satoshi, Kasumi, Takeshi, Kenji and their Pokemon song), and was reminded of different instances in other anime the seiyuu of Brock and Tracey interacted. I realised those characters tended to be enemies... Fushigi Yuugi: Seki was Chichiri and Ueda was Amiboshi and Suboshi. Chichiri was part of the Suzaku Shichiseishi while the twins were part of the Seiryuu Shichiseishi, which resulted in them being enemies. Fruits Basket: Seki was Kyo and Ueda was the Student Council President (at least until graduation). SCP didn't get along with Kyo at all because of his (natural) appearance and behaviour. Weiss Kreuz: Seki was Ken and Ueda was Kase. For me, this is the most heartwrenching. Ken and Kase were friends until Ken was banned from taking part in football following a "drug scandal". Kase acted like he was on Ken's side. We later learn that Kase was part of the whole setup. He claimed he was jealous of Ken. Ken tried to believe Kase was a good guy, but when Kase shot him twice (once when he finally told Ken everything, the next time when Ken went to kill him), Ken shed a tear in dismay before giving the finishing blow. Kase's last words to Ken were "I'll see you in Hell" before his life leaves him. Ken's response was "No, because we're already in Hell". And of course in Pokemon, they briefly interact as Kenji/Tracey and Takeshi/Brock. While in canon they get along well, there are some fans who make their own non-canon "they actually hate each other" materials. Oh, and in the dub, tune into any series by 4Kids/CPM to hear their VAs Ted Lewis and Eric Stuart interact in multitude of ways: friends, rivals, bitter enemies, even family.