Monster Blood

Monster Blood is a green substance that is similar to a mixture of Mars Mud and Silly Putty.

In the Monster Blood canon, it has a spell put on it that makes it consume things (whether animate or inanimate) it envelops. In addition, anything and anyone that consumes the Monster Blood will grow huge like a giant.

The Books
Monster Blood first appeared in the book, Monster Blood, where it is found in an old toy store in a dusty metal can which is opened by Evan Ross and Andy. Soon afterwards, Evan's dog Trigger eats some and grows very large. It only does this because there is a spell put on it by a young witch named Sarabeth.

In Monster Blood II, Evan initially has a dream involving his dog Trigger. In the dream, he notices Trigger has eaten Monster Blood. Soon after having this dream, only now in waking life, Cuddles the class hamster, eats some Monster Blood. Evan is then forced to eat some also in order to combat the gorilla-sized hamster. At the end, when the Monster Blood's expiration date kicks in, Andy gives Evan some more from Europe and Cuddles eats some more and the book ends.

It was in Monster Blood III that Evan and Andy come up with a plan to get Kermit back with Monster Blood for getting on their nerves. Their plan goes wrong and Evan accidentally swallows some and grows at least two stories high. He then sticks Conan up a tree and plays a game of softball, though this doesn't last long, as he is a highly visible and unusual sight at his new height, attracting public attention. The police and fire department soon come, thinking he is an alien threat. Eventually, Kermit makes a formula at home which causes shrinking, allowing Evan to drink it. Evan wakes up the next day and is the size of a mouse.

Finally, for the last book in the Goosebumps book series, Monster Blood IV, where it comes in a can, but is blue, and multiplies when exposed to water. The blood is also carnivorous, evil, and has fangs. This blood is actually not a toy at all, but an aquatic military super weapon. The blue Monster Blood also makes a person multiply, when someone eats it.

Then in the third Goosebumps HorrorLand book, Monster Blood for Breakfast!, the Monster Blood was a "12 hour Trial Strength" version. It came in a plastic egg and made a new character, Matt Daniels, grow about nine feet tall. It then followed him to HorrorLand where it sucked up Sheena Deep and a horror named Byron who saved Matt and Sheena's brother, Billy.

It also appeared in the television episodes, Monster Blood and More Monster Blood, where airline food makes it shrink. It will only stop growing when it is put back in its jar. If a person eats it, they had better make sure some of it gets on their clothes; without doing so, their clothes will rip off if they continuing growing. 

Personality
Monster Blood has a very enormous appetite and would always swallow anyone or anything that gets in its way. However, the Monster Blood can never last forever as its magic would always wear out on an expiration date and if someone thought of a cure for its effects. But every time one opens the Monster Blood, they are doomed and are in even more trouble if they swallow it.

Appearance
Monster Blood is a slimy green substance that is usually either cold or hot. And on the covers, it has a face.

Variations
Asides from the ordinary Green Blood, there actually are also other variations of slime that are used in a similar fashion:
 * Purple Peanut Butter, which has the opposite as the original (Shrinks the consumer instead of enlarging him/her), It gets its name from its color and peanut butter-like smell.
 * Blue Monster Blood, Which multiplies whenever it contacts water. Anything that consumes it multiplies and becomes meaner.
 * "12 hour Trial version", which basically was a "watered down" version of the original effects.
 * "Vampirism Goo" (AKA Vampire in a Can): A red Monster Blood-like goo that turns whoever consumes it into a vampire. It actually has no legitimate relation to Monster Blood, but it works in a fashion much similar to it.

Books

 * Goosebumps
 * Monster Blood
 * Monster Blood II
 * Monster Blood III
 * Monster Blood IV (daydreams and nightmares only)
 * Goosebumps Series 2000
 * Return to HorrorLand
 * Goosebumps HorrorLand
 * Monster Blood for Breakfast!
 * Who's Your Mummy? (coin cameo)
 * Give Yourself Goosebumps
 * Escape from the Carnival of Horrors
 * Beware of the Purple Peanut Butter
 * One Night in Payne House (mentioned)
 * Goosebumps Presents
 * Monster Blood
 * Classic Goosebumps
 * Monster Blood

Television and Film

 * Television series:
 * Season 2 - Monster Blood and More Monster Blood
 * Movies:
 * Goosebumps (2015 film) (mentioned)

Video Games

 * Goosebumps: The Game

Trivia

 * The Monster Blood is the first antagonist in the series to appear in a sequel and become a recurring character.
 * The Monster Blood was the first antagonist to not speak.
 * In Monster Blood II, it is revealed that Monster Blood has an expiration date, causing the magic to wear off. This is the only known way to defeat the Monster Blood (in the books).
 * In Monster Blood II, it is revealed that Monster Blood is sold in Europe (Germany).
 * In the television episode, the Monster Blood seems more sensitive to the touch and bouncy
 * In the television episode, the Monster Blood was a substance created by Sarabeth, while in the book it was a normal toy that had a spell put on it.
 * Monster Blood also appears in the Give Yourself Goosebumps books, Escape from the Carnival of Horrors and Beware of the Purple Peanut Butter. It is also mentioned as a puzzle in One Night in Payne House (the reader needs to know the color of Monster Blood, in order to solve something.)
 * The blood in Monster Blood IV is not the regular Monster Blood, but actually an aquatic military super weapon. This blood multiplies when it is exposed to water and more resembles slugs or snails than slime. The blood has eye stalks, and mouths with razor sharp teeth. However, like the original Monster Blood, if you eat it, you will change, as you become mean, can't stop drinking water, and multiply when you eat the blood in Monster Blood IV.
 * In Monster Blood for Breakfast!, the monster blood comes in a plastic egg like silly putty.
 * The green Monster Blood shares many similar qualities with the alien from The Blob and the 1988 remake of the same name.
 * The green Monster Blood was speculated to appear in the 2015 Goosebumps film. It was speculated to be one of the monsters unleashed by Slappy. However, Dylan Minnette (the actor who's playing Zach Cooper) confirmed that the Monster Blood will only be mentioned in the movie.
 * The Monster Blood shouldn't grow after the first book since Sarabeth, the witch who cursed the Monster Blood, dies at the end of the end of the book. This causes the Monster Blood to shrink. This means that the books Monster Blood II, Monster Blood III, and Monster Blood for Breakfast! shouldn't grow or be able to make things giant. Even if Sarabeth curses all the Monster Blood in the world, all the Monster Blood would shrink away.