Monster Blood IV

Monster Blood IV is the book number 62 in R.L. Stine's Goosebumps series, and this book concludes the original "Goosebumps" series, preceding its "2000" series.

Plot Summary
Evan Ross must stay at his nerdy cousin Kermit's house while his parents are gone. Andy discovers a can of Monster Blood; unfortunately, this variety of monster blood is blue rather than green (it's revealed later that the Monster Blood is actually a failed military experiment for use in underwater attacks). It turns out to be a new breed of monster blood, which then drinks water and explodes into two. The creatures explode over and over again until there are sixteen. They get captured, and Kermit puts them in an old bathroom no one uses. Inside the bathroom, they drink more water and multiply until there are thousands. They get loose and attack the town. After they are defeated, Evan's bully, Conan, eats some and multiplies into four different extremely mean Conans.

Tagline
This blood is bad to the bone!