Yes, yes, I know that a live action Homestar Runner movie would never work and would pretty much be the most terrible thing in the history of ever.
But just for argument's sake, let's talk about what actors could represent each character.
Homestar: Ashton Kutcher, Brendan Fraser or some other jock guy who can play stupid
Marzipan: Kate Hudson, she seems like a hippie
Strong Bad: This one is difficult. Probably some comedian like Ben Stiller or Adam Sandler could ham it up and do the voice passably. The only person who actually sorta reminds me of Strong Bad is Will Arnett (Gob from Arrested Development.)
Bubs: Definately Cedric the Entertainer
Coach Z: Jamie Kennedy, or Hank Azaria
Strong Mad: Some huge wrestler guy.
The KOT: Richard Riehle, he's an obscure character actor, but he's basically a human version of the KOT.
http://www.buffytvs.de/btvs/Serie/Charaktere/Pics/merrick_s.jpg
Strong Sad: This one has been pretty impossible to think of a good answer for.
Homsar: Kelsey Grammar, just for the inside reference.
Any other ideas for who could represent the characters?