The Colonel Sanders (full name Harland David Sanders) was a man known to be the founder of the fast food chain KFC. In SuperMarioGlitchy4's videos, he appears in "Spells n' Wiztards" and The Mario Channel: MARIOBUSTERS.
In Spells n' Wiztards, the Colonel Sanders was summoned by Steve, who cast a spell on a chair when he was learning spells at Hobowarts, a wizard academy inspired by Hogwarts from the Harry Potter series. The Colonel was singing the song "My Milkshake" while dancing... or something, shocking SuperMarioGlitchy4 and SuperMarioGlitchy3, who were fighting each other at the same moment.
He later reappeared in the same video, in a spell competition held by Dumbledore. He was recreated that time by SMG4 who had to transform a Rock into a chicken. SMG4 missed and created a Colonel Sanders holding a KFC bucket, instead of a chicken.