Boy, it's so real, I even feel like a werewolf.
After its twin successes with 1957's I Was a Teenage Werewolf and I Was a Teenage Frankenstein, it's only natural that AIP would want to pair up its two monstrous creations, Universal-style. And it did so the following year in How to Make a Monster, albeit in the form of the fictional (and generically titled) Werewolf Meets Frankenstein being produced by American International Studios (which not only has its own lot, but also a proud history going back 25 years). When veteran makeup man Robert H. Harris is given the shove by the new regime that has taken over the studio, though, he fights back by adding a special ingredient to his foundation cream that gives him influence over the actors playing the Teenage Werewolf (Gary Clarke, taking over for Michael Landon) and Teenage Frankenstein (Gary Conway, reprising his role from the earlier film), who are then dispatched to murder the new studio heads, who only want to make (ick) musicals. Naturally, this attracts the attention of the police, who turn the heat up on Harris's nervous assistant (Paul Brinegar) after the monstrously made-up Conway is spotted running from the scene of one of the crimes.
The funny thing about the film, which was shepherded by Teenage Frankenstein director Herbert L. Strock, is while Harris starts out extremely mild-mannered, over time he becomes more and more of a raving lunatic. And things take a definite turn for the macabre when he creepily invites Clarke and Conway over to his house (where the film switches from black and white to color) so he can immortalize them as he's done with his other creations, which are displayed in a room populated by props from previous AIP films. Suffice it to say, whatever his actual plans are (the dialogue is vague on that point, but I think it's something along the lines of what Vincent Price does to his victims in House of Wax), the boys are right not to want any part of them.