The partnering up theory is kind of interesting. It's interesting to note that in book 5 Petunia refers to "that awful boy" telling Lily about Azkaban and Harry (and most likely the readers) assume she's referring to James. But that's only implicit. I read somewhere someone theorizing that the awful boy was Snape that Petunia overheard 'cause she and Dumbledore were the only ones who stuck up for him. Dunno whether to believe it or not though.