While performing as a company player with the Groundlings for a number of years, Parnell began doing commercials and getting guest roles on various sitcoms, such as "Seinfeld" and "Murphy Brown". He was hired to join the cast of "Saturday Night Live" as a featured player, and debuted on the show on September 26, 1998. He was promoted to repertory player the following season. In the summer of 2001, because of budget cuts and the hiring of four new cast members, Lorne Michaels was required to dismiss two cast members; he chose to lay off Parnell and Jerry Minor over Horatio Sanz, Rachel Dratch, and Maya Rudolph, but Parnell was rehired in the middle of the following season.