While we all claim to have loved G.I. Joe: The Rise of Cobra when we were younger, there should be no embarrassment to admitting that you can't remember all the characters. I mean, there were a ton and, unlike Exosquad, none of the Joes seemed to die. Taking this fact into account, Paramount was sure to release some sort of character guide so we knew who was who.
G.I. Joe: The Rise of Cobra Character Guide
To catch up on the G.I. Joe characters (featured in the film), head on over to Yahoo. To be quite frank, you might have better luck learning about these characters at Wikipedia, as the Yahoo report is pretty vague. Check out the Snake Eyes summary:
In a not-so-surprise move, the filmmakers have kept Snake Eyes' outfit accurate to his cartoon appearances. Aside from a distinct lack of pet wolves, this is the Snake Eyes we know and love, alternating between a sword and a gun as he tries to cut his way through Cobras.
Eh, I guess it is just a refresher, so check it out here.