Oscar the Grouch made an appearance as part of The Mob in several consecutive episodes in the second season, from January 11 to February 22, 2008. Among the other celebrities appearing during Oscar's run were The Tonight Show's Ross the Intern and Evan Marriott, the original Joe Millionaire.
In another episode, Saget accidentally refers to Oscar as "Grover," and then as "Cookie Monster" just to fool around. Oscar later gets back at Saget by calling him "Howie" (after Howie Mandel, the host of another popular NBC game show, Deal or No Deal).
In the final installment, Oscar misses the question "Alphabetically, which number comes first?" with the correct answer being 24. This leads to a humorous conversation in which Saget asks if it isn't what Oscar and his fellow Muppets do on Sesame Street, to which Oscar replies that only knows the number of letters in the alphabet. He also remarks that the Dahm Triplets like him. The audience even claps when he is eliminated.