Johnson joined the cast of MADtv in 2005 as a feature performer, for the eleventh season. She became the third black female cast member in the show's history (Debra Wilson and Daniele Gaither were the first two respectively). She was promoted to repertory status for the show's twelfth season. Frequently recurring characters include Ka-Son and Darrell, while her impersonations include Condoleezza Rice, Oprah Winfrey, Queen Latifah and Randy Jackson.