It seems Greg began using the Joker character in his videos around 2010 or 2011. The character seems to be consistently popular with fans throughout the years. Greg uses the character quite frequently in videos over the years.
Greasy green hair slicked with a side part, messy clown face makeup, and the iconic purple and green suit are all used by Greg.
The voice and mannerisms Greg uses when portraying the Joker are ripped right from Heath Ledger's portrayal of the character in The Dark Knight movie trilogy.
Greg usually uses the Joker in goofy roles in his comedy videos, although sometimes he will use the character in more serious sketches. An example of this is his 2011 video "I Was Drugged", where he, as the Joker, drugs and kidnaps a junkie (played by then fiance Shiloh) and transforms them into Harley Quinn, Joker's devoted female sidekick.