Hotel Transylvania: Transformania - What We Know So Far

Audiences can easily discern the film's plot from both trailers. By the looks of it, Dracula refuses to fully accept Johnny as part of the family due to his inherent humanness. That's when Professor Van Helsing promises Johnny the opportunity to become a monster like his father-in-law has always wanted. The experiment's a success with Johnny transforming into a dragon, but the process has unintended side effects. Johnny may be a monster, but Dracula and many of the monsters at the hotel turn into a bunch of average Joes.

The plot will likely revolve around all of the main characters trying to get everything back to the way they were with Dracula and his crew at a serious disadvantage now that they can't utilize all of their powers. Of course, there will be plenty of gags along the way, most notably with everyone realizing the Invisible Man has been naked this entire time. 

Considering this is the last film in the franchise, it would make sense for loose plot threads to receive closure. Now that Dracula has to walk a mile in Johnny's shoes, perhaps he'll finally come around and accept him as part of the monster family.