Trivia: Slimer had no name in the first Ghostbusters movie, but the producers nicknamed him "onionhead" because of his awful smell. He was named Slimer in the cartoon series "The Real Ghostbusters." The name came from the scene in Ghostbusters where Ray shows Winston the containment unit and says, "This is where we store all the vapors and entities and slimers we trap." Since Venkman was slimed in the hotel, they decided to name the ghost that did it Slimer.
Trivia: Oscar is actually played by twins, Hank and Will Deutschendorf. These boys are the nephews of the late singer John Denver (formerly Deutschendorf). The boys are John's brother Ron's children. Tragically, Hank passed away in 2017, after a prolonged battle with schizoaffective disorder - a serious mental-health illness he had been struggling with for years.