The bloop was a primate similar to a terrestrial chimpanzee, native to the planet Preplanis from Lost in Space. It had a conical head with thick hairy antennae and was named for the sound it made.

Penny Robinson acquired a pet bloop that she named Debbie. ("Island in the Sky") There was also another bloop named Debbie in the unaired pilot episode of the show that Penny befriended. ("No Place to Hide") Due to the change in plot between the two episodes, these are assumed to be different bloops.

The animal the Robinsons find in the Lost in Space motion picture is nicknamed the "blarp".