Sir Isaac Newton is a historical figure who makes a non-canon appearance.
Homer calls the Marital Stress Hotline in desperation as he fantises over his co-worker, Mindy Simmons. After he realises the call was from Ned Flanders, he abruptly hangs up and accidentally is knocked out by toppling the phone booth over. While knocked out a ghost, or his conscious picks up Homer. However, Homer does not recognise him, so he morphs into Colonel Klink.