Jay Leno is back to performing punchlines at the top of the Tonight Show. Leno is returning for a special appearance on Tuesday's episode of his old show to deliver the opening monologue, subbing in for current host Jimmy Fallon. Leno's final episode as host of the venerable NBC late-night show aired in February 2014, with Fallon taking the reins later that month. Leno's new show, Jay Leno's Garage, debuts Wednesday at 10 p.m. on CNBC.