While it's obvious Lindsay Sloane and Melissa Joan Hart aren't playing, Nate Richert is actually drumming in the first song.
John Ducey, who played Dwayne Kraft, went on to play Leonard, Sabrina's coworker in the later seasons of Sabrina.
The song that Sabrina, Harvey and Valerie perform is Blondies "one way or another." Blondie lead singer Debbie Harry starred in the pilot episode of Sabrina the Teenage Witch as a member of the witches council.