Evan and Andy come up with a plan to get back at Evan's cousin Kermit with Monster Blood for getting on their nerves. The Monster Blood saga continues in the twenty-ninth Goosebumps book. After dinner, Evan and Andy discover Cuddles eating from the new can of Monster Blood. Following this, Andy gives Evan a can of Monster Blood her parents got from Europe (Germany). Eventually, the Monster Blood's expiration date kicks in, shrinking Evan and Cuddles back to normal size. Evan consumes some Monster Blood himself in order to take down the gorilla-sized hamster. Soon after having this dream, only now in waking life, Cuddles the class hamster, eats some Monster Blood, making him grow to a ridiculously large size.

Evan initially has a dream involving his dog Trigger where he has eaten Monster Blood. Monster Blood returns in the eighteenth Goosebumps book. Later when Evan and Andy go to collect it, they find that it mysteriously vanished. She meets her demise when Trigger knocks her into the huge mass of Monster Blood, which causes it to shrink to a puddle. It's later revealed that the Monster Blood's abilities were caused by a spell cast by a witch named Sarabeth. The Monster Blood itself grows larger and larger as the story progresses, eating several objects and even a couple people.

Soon after Evan and Andy open the Monster Blood, Evan's dog Trigger eats some and grows very large. It evolves and becomes warm, sticky, and bubbling. It's innocuous at first, cool to the touch, glowing, stretchy, and bouncy. It is found in an old toy store contained in a dusty metal can opened by Evan Ross and Evan's newfound friend Andy. Monster Blood makes its debut in the third Goosebumps book.

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