Fox is the leader of Star Fox, who is the archrival of Star Wolf. He is in love with another member of Star Fox, Krystal, whom he saved in their last adventure. In multiplayer mode he is the all around player, good for players who are starting.
Slippy is the team's inventor, and over the years he has invented many useful items, such as the Landmaster, Blue Marine (Star Fox 64), and the shields that the Star Fox team uses. He is also Fox's best friend. In multiplayer mode, he has a higher jump than most, has good skill with a Landmaster and his basic weapon has a faster charge rate.
Peppy was a member of the original Star Fox team, which consisted of Peppy Hare, James Mcloud, and Pigma Dengar. Although he has now retired, you can unlock him for multiplayer mode. He has the highest jump and can charge his blaster four times as fast.
Krystal is the newest member of Star Fox, joining after Fox saved her in his last adventure. She is the weakest character by far in multiplayer and specialises in nothing. Her only good point is that she respawns with two shields.
Falco is the mysterious, rogue member of Star Fox, and has left them from time to time, coming back just in the nick of time to save them. A bit obnoxious and cocky at best. In multiplayer mode he is the fastest character and best with the Arwing. He does have a poor HP level though.
The leader of Star Wolf and Fox's arch nemesis. Not much is known about this shadowy character. Easily the best character in multiplayer mode, his stats greatly surpass everyone else.