Some of Stack's early roles include appearances in shows such as Days of Our Lives, Benson, Laverne & Shirley, Remington Steele, Night Court, and ALF among others.
Stack then played Notch Johnson on Son of the Beach, a Howard Stern-produced Baywatch send-up which aired on the FX cable channel from 2000 to 2002.
Stack has appeared in many films including Back to School (1986), Clifford (1994), the principal in Idle Hands (1999), Cast Away (2000), Dumb and Dumberer: When Harry Met Lloyd (2003), Scary Movie 3 (2003), and American Pie Presents: Band Camp (2005).
In the sketch, Stack plays a fictional cable news reporter who interacts with customers at gas pumps-–sometimes completely taking people off guard.
Stack also acted out a fictional version of himself on the television program My Name Is Earl, in which he was depicted as an arrogant, depressed, alcoholic resident of Camden County who frequently hosted beauty pageants and parades.