Kenan Thompson is one of the best cast members “Saturday Night Live” has ever had. It’s not his first ensemble sketch comedy. He starred as a kid on “All That,” which Nickelodeon spun into “Kenan & Kel” with Kel Mitchell. That TV show was so successful it spawned “Good Burger” (1997) where Kenan and Kel are part of a ragtag team of workers at a fast-food restaurant. The dopey plot is pure Nickelodeon sitcom junk food, but watching these two 19-year-olds trade snappy banter makes you understand why Thompson’s career took off and makes you wonder what happened to Mitchell.