Hasbro loves doubling their money by taking a character, repainting it, and calling it another character. (Although the first Bumblebee they didn’t even bother coming up with a new name.) In the case of Prowl, Bluestreak, and Smokescreen they tripled their money by reusing the same mold three times! This continues to this day because hey, why not? It’s easy money.
I’m not sure if Inferno is the repaint of Grapple or Grapple is the repaint of Inferno. Either way, they’re the same basic mold except Grapple is orange with a crane hook and Inferno is red with a fire truck ladder. Inferno appeared more in the second season of the show than Grapple and probably a few times in the comic book. He had a Generation 2 toy reissued while Grapple did not.
Inferno was often paired with Red Alert, who was a repaint of Sideswipe, a Lamborghini Countach. Red Alert was painted white and red instead of red and white and some Fire Chief stickers slapped on—because so many fire departments drive around in Lamborghinis. (Maybe in Italy?) Anyway, Inferno’s primary job of putting out fires was eventually taken by the Protectobots, who had their own fire truck with Hot Spot. Like many Autobots he pretty much disappeared after the 1986 movie.
Besides the Generation 2 toy, Inferno has had other reissues. He’s probably appeared in the IDW comics, but certainly hasn’t done anything all that memorable.
Besides reusing models, Hasbro also likes to reuse the names of characters. Part of that is for trademark reasons, as they wouldn’t want Mattel to be able to come out with a new toy called Optimus Prime, so they make sure to have new Optimus Prime toys every couple of years.
For the second series of Beast War toys, Hasbro came up with a red ant called Inferno. You know, fire ant, Inferno? Heh. The character was introduced about midway into the Beast Wars TV show's first season. During his programming something got messed up so that Inferno actually thinks of himself as an ant. He thinks Megatron is his “queen” and the Predacon base is “the colony” so that he often shouts “defend the colony!” That made Inferno a pretty amusing character and more remarkable than the fire truck Inferno. Appropriately for a fire ant, Inferno's main weapon is a flamethrower. If Inferno got into a fight with the other Inferno the Beast Wars one could start fires that the Autobot one would put out.
I don’t think this Inferno has really been reissued or appeared anywhere besides the Beast Wars TV show. A funny quirk with his toy is that his ass opened up into a jet engine to let him fly. Do ants fart? That might be what’s powering that engine then.