Dupe or not, there's just something for the ages in having Mr. McManus singing "I wanna bite the hand that feeds me" while a furious Lorne Michaels is just off-camera, being held back by crew members...
Learn something everyday. I've seen this episode of SNL a dozen times and just figured that this was just some ham-handed attempt by Costello at humor, as the guest bands did occasionally try to be "funny" just like the cast. I didn't know there was a story behind it.