The Cameo: Hulk Hogan appears in the sequel, threatening to beat up the Gremlins after they interupt their own movie. Bugs Bunny and Daffy Duck also show up at the beginning and the end of the film.
Doing It for the Art: Legendary Oscar-winning special effects artist Rick Baker was convinced to work on the sequel by letting him completely redesign the mogwai/gremlins, including making the new hybrids.
Playing Against Type: John Glover is best known for playing villains and changed Clamp to more friendly because he disliked being exclusively cast as bad guys.
What Could Have Been: The original script of The New Batch featured Randall Peltzer making a Cameo at the end of the movie with his latest invention — a wetsuit-type device to prevent Gizmo from ever getting wet again.
The first movie was going to be Darker and Edgier. Gizmo was going to become a gremlin in the second act, but this was deemed too confusing to audiences. Billy's mother was also going to be murdered by the gremlins, with her head rolling down the stairs. Additionally, Billy would have been your typical 80's Hollywood Nerd and not only traveled around the town with two companions during the madness (a love interest and a bully-turned-emergency-ally), but wielded a sword. He still wields a sword in the final film but it's limited to only one scene. As to his companions, presumably they morphed into Kate and Gerald.
In the same vein, Mr. Hanson's death was originally nastier and involved lots of needles, until it was changed to just the one syringe in his butt.
During production of the sequel, there were plans for an animated series. There was even a blurb for it in the He's 50, Folks magazine celebrating Bugs Bunny's 50th anniversary. Unfortunately, the poor box-office performance of the sequel resulted in the television series getting canceled.
There were going to be more Mogwai in the sequel, one of them a female that could have served as a possible Love Interest for Gizmo, but they were ultimately deleted. However, NECA released figures of the scrapped Mogwai recently. Also, there were going to be more mutant gremlins as well, including an elephant-gremlin hybrid, but were left out in the end.
Pat Hingle and Emilio Estevez auditioned for the roles of Rand and Billy Peltzer. On the DVD commentary, Joe Dante praises Hingle's screen test as a Frank Capra-esque character who realizes that his best days are long behind him as being too good for the movie, because he would have stolen the show from Gizmo and the gremlins had be been cast.
Word of God: Mohawk is effectively a reincarnation of Stripe.