Maniac Mansion - Season 2 Episode 9 The Attack of Killer Keifer

Fred finds a book in the lab called ""My Forbidden Experiments"". He decides to perform one of them, and creates an odd slime creature which he doesn't know about. When looking for his headphones, the slime attacks Keifer and makes him act strange. Now all Keifer wants to do is help out Fred in the lab on an experiment that absorbs oxygen. Fred figures out that Keifer is now an alien creature who wants to get rid of all the oxygen on earth. Fred then tricks him into the andromeda chamber, and changes him back to normal.