Real Neme:Slimer
Publisher:Now
Slimer is a very well-known figure from the Ghostbusters Universe and although he began as an antagonist he quickly became an ally of sorts to the team as well as a mascot - Slimer resembles a floating mass of green goo and indeed gets his name from his special ability to cover anything he flies through with a layer of ectoplasmic "slime": he was infamous for being the ghost that "slimed" Peter Venkman, an event Peter did not forget.
Although mischievious and extremely greedy Slimer is notable for being one of the few ghosts in the series that is not truly malevolent, he is happy to live amongst humans and scares fairly easily - he also doesn't get along very well with other ghosts, perhaps due to his benevolent nature.