Karloff "The Menace" Mennis is a fictional character that made his primary debut at the end of the eleventh Goosebumps HorrorLand book, Escape From HorrorLand. He is the owner of Panic Park and was the primary villain in The Streets of Panic Park. He has a second face, which The Menace got after travelling through a two-way mirror.
The Menace performed extreme experiments on making scary rides which resulted in a variety of accidents including a roller coaster that fell off its track and crashed into some parked cars. The Menace claimed to have turned the riders brains into mush with the wind. But it turned out he had been lying to prevent the children from returning to HorrorLand.The Menace turned half of Matt's face into a monster's face, turned Robby invisible, turned Billy and Carly Beth into shadow people, and hurt Jillian and Jackson.
All of the villains throughout the series except Monster Blood, Mrs. Hardesty, and the evil camera began to collaborate under The Menace to try and get revenge on the children. In The Streets of Panic Park, The Menace tried to get the children fear level up to 100 on the Fear Meter.
If The Menace were to achieve that goal, then Panic Park would return to reality. The Menace's plan was to never let the villains or the children escape, if he were to return Panic Park to reality. In the end, the villains formed an unlikely alliance with the children to stop The Menace from achieving this goal.
They did this, by making the children's fear level return to normal by making them laugh. As it turns out, Panic Park was shrinking as the children's fear meter reduced. The Menace then informed the children that if Panic Park were to reduce so far to the point of disappearing, everybody would disappear along with it.
The Menace encouraged the kids to spill out their fear about how they could shrink along with Panic Park, but the villains come in and Slappy constantly insults the Menace and makes the kids and the villans laugh, causing Panic Park to finally shrink.
The children ended up going on the Whirlwind to take the path back to HorrorLand. Once they came back, they met up with their parents and returned home, almost as if nothing had ever happened.
- His first name is a reference to horror star, Boris Karloff, who is famous for his roles as the Monster from Frankenstein and Imhotep from The Mummy.