A big personality can go a long way on the big screen, and can even help hold up the sagging end of a far less gregarious character. But there's no way to go but down when two boring personalities are paired up. Case in point: Natalie Portman and Hayden Christensen in the later Star Wars films. It wasn't all their fault; they've both delivered far more exciting and impressive performances in other movies. Let's just blame George Lucas. Because, Jar Jar Binks.
Don't: Match wood with cardboard.