Ben Stiller as Grumio because Grumio is Petruchio's servant, so they would need some sort of bond. Owen Wilson and Ben Stiller have worked together several times like in "Zoolander" and "Night in the Museum," which has made them extremely close friends. Seeing as Owen and Luke are brothers, Ben Stiller and Luke Wilson have bonded over time- which creates a good enough bond for them to really do well at their roles, Grumio and Petruchio.
Luke Wilson as Petrucio because due to his performances, you know he can deal with any type of woman while keeping his cool. Petruchio would need patience and drive to tame Katherine, both assets that Luke Wilson has.
Owen Wilson as Hortensio because I casted his older brother, Luke Wilson as Petruchio- and this makes sense for two different things. In the play, Petruchio and Hortensio are good, lifelong friends, so the fact that they're brothers in real life would give them that great bond and chemistry between them. Also, Owen Wilson is the younger brother so it makes sense that he would go for the younger sister, Bianca and Luke would go for the older sister, Katherine.
Josh Hartnett as Gremio because he's young enough and handsome enough to keep up with somebody like Megan Fox. So in terms of the play, Gremio could be a good possible match for Bianca.
Wilmer Valderrama as Tranio simply because I casted Ashton Kutcher as Lucentio. Ashton and Wilmer have a close bond from acting together for years on the television series "That 70's Show." That all matters because Tranio is Lucentio's servant, and I think that Wilmer is the less famous one in their relationship so I chose him as the underdog.
Ashton Kutcher as Lucentio because he is young and attractive, yet intelligent. Even though his career as an actor was a success- he did go to college in Iowa meaning he did seek education, as did Lucentio.
Megan Fox as Bianca because she is
untouchable. Many people find her attractive and many people wish they could date her and so forth. She has a lot to offer, just like Bianca does. 
America Ferrera as Katherine because of her appearance (as Ugly Betty.) Also in the movie, "The Sistorhood of the Traveling Pants," her character is catty and dramatic- just like Katherine is.
Denzel Washington as Baptista because he is a strong man that seems like he doesn't take no for an answer. He carries himself well and people respect him for that, much like Baptista's children and peers respect him.
