Really? That's surprising. I saw Tasuki's voice actor under a different name, so I didn't think that they were the same person. Now that I think about it, Cosmo's early season voice, the one that I thought was fine, does sound like a more hyperactive Tasuki. I also think he voiced a random bodyguard in one episode of Disney's The Replacement and it did sound exactly like Tasuki.
I also agree with Mark Hamill being the Joker. I haven't seen much of the Star Wars movies, so I didn't associate him as Luke Skywalker. Though, from the bits I have seen from the movies, it's really surprising to see him being the typical good guy to voicing such a dangerous and awesome villain.
Eric Stuart, the original voices of Brock and James from Pokemon and Seto Kaiba from Yu-Gi-Oh!, has his own band called the Eric Stuart band.
In terms of Japanese voice actors, Rica Matsumoto, the voice actress for Satoshi/Ash in the various Pocket Monsters series, also voiced Bakura in Yu-Gi-Oh! Duel Monsters.