Tunnel Rat was one of the collection of new
G.I. Joe characters premiered in the big 1987 G.I. Joe movie (the animated one where it turned out that
Cobra Commander was from some secret underground civilization).
The group of characters, called the "Rawhides" in the film (probably because they were
raw) seems like something of an effort to make a microcosm of weird diversity. Not simply
ethnic diversity, but in character weirdness. In addition to Tunnel Rat, there's a hot ninja girl codenamed
Jinx, who for some reason fights best when
blindfolded; a
basketball player codenamed Big Lob, who inexplicably speaks almost exclusively in third-person sports patter; literally a cop codenamed
Law with a dog named
Order (I'm going to go ahead and presume that the dog doesn't have a "real" civilian identity); and Lieutenant Falcon, who (if you know the regular series characters) is the newly-introduced half-brother of longtime Joe's mainstay
Duke. Falcon is voiced by the legendary
Don Johnson. Tunnel Rat had no such luck, coming from some little-known actor.
Obviously, Tunnel Rat's thing is that he's the best there is with tunnels or some shit like that. During training, he navigates the deadly obstacle course set up by the trainer by finding a tunnel that just happened to run from near the beginning of the course to just after the end. What skill!! Naturally, later on in the film it turns out that the way to enter the Cobra base and save the world and all that is -- you're not going to believe this -- discovering a tunnel leading into the base!!
You'll be forgiven if this is the first you've ever heard of this character, and if you never think about him again after this.