CBR lists their best drop-in sitcom characters. They left off a lot of great ones but let's see what you think.
https://www.cbr.com/best-drop-in-sit...-benson-icarly
10. Freddie Benson (iCarly)
09. Stanley Zbornak (The Golden Girls)
08. Benny (The George Lopez Show)
07. Frank & Marie Barone (Everybody Loves Raymond)
06. Dean Pelton (Community)
05. Shawn Hunter (Boy Meets World)
04. Cosmo Kramer (Seinfeld)
03. Howard (The Bob Newhart Show)
02. Steve Urkel (Family Matters)
01. Cousin Itt (The Addams Family)