Too start off, let's go with the cast from the first film
Justin Chatwin - Goku
Emmy Rossum - Bulma
Chow Yun Fat - Roshi
Joon Park - Yamcha
James Marsters - Piccolo
AND NOW, THE CHARACTERS FOR THE SEQUEL...
J.J. ABRAMS - DIRECTOR
Loved star trek, seems to have that creativity dragon ball needs
ZAK PEN - WRITER
Great at writing super hero films
HANK AZARIA - KING VEGETA (CAMEO)
I don't know why Hank, he has that look and no doubt a good actor
SHAOBO QIN - KRILLIN
You're not gonna find an actor that is better for krillin, he's got that look and i like his acting
TIMOTHY OLYPHANT - TIEN
He looks a lot like Tien when he is hairless, (HITMAN) his acting is quite good, One of my favourite movies is Hitman.
RAY PARK - RADITZ
Once a good choice for Vegeta, but now a better choice for Raditz, he's a great actor, loved him as Darth Maul.
NATHAN JONES - NAPPA
Look at him there, looks a lot like Nappa, i've never seen him act, however, if someone looks like the character they are portraying, then they're fine in my books!
MATT MULLINS - VEGETA
A Great marital artist and a hell of a look a like to Vegeta, I can't see anyone else playing Vegeta then Matt Mullins
ANDY SERKIS - FRIEZA
Now, frieza will be totally CGI, however, Andy Serkis could easily portray him on set.