BOB

BOB (short for Bicarbonate Ostilizene Benzoate) is a blue, indestructible, one-eyed gelatinous mass, spontaneously created in a laboratory when scientists injected chemically modified ranch dressing into a genetically modified tomato. He has the ability to absorb anything, can assume any shape, has no brain, and digests objects in seconds (depending on their size). He can also extend his body and detach his eyeball. He was captured in 1958 and sent to Area Fifty-Something. Sometimes, he can be quite stupid due to his lack of brain. He makes many mistakes, from confusing certain holidays to accidentally launching missiles from the base by pressing the launch button, thinking it was the "Lunch" button. He also has a tendency to get confused in certain situations, but he often finds a way out of anything. It is unknown how far BOB can stretch his entire frame, but he is seen to be very long in the film after helping himself and the other monsters reach the core of the spaceship when the Clones attacked them. It is almost proven that he is resistant to physical attacks, as he defended Dr. Cockroach from the attacking Alien, but managed to remain stable after taking a punch to the eye, which ricocheted back and forth, hitting the Alien. It is possible that he is resistant to energy and mental attacks due to his unique physique and lack of a brain, but this has not been proven. BOB can greatly increase the amount of his slime, expanding enough to fill a large swimming pool (Maximum BOB) and grow dozens of arms and extend them to great lengths (Came... on a Field Trip).
He can absorb an extremely powerful blast, strong enough to destroy Area Fifty-Something and a vast portion of the surrounding desert, by containing it within his body (This Ball Must Be Dodged).
It can survive without oxygen and is immune to the vacuum of space.