"John Madden Popcorn Popper Commercial" - The start of Frank Caliendo's hilarious Madden impersonation.
"When Babies Attack" - Perfect send-up of all those terrible (mostly Fox) prime-time "When [Insert random noun] Attacks" shows.
"Kenny Rogers Jackass" - Single Greatest Line in all of TV history: "I'm Kenny Rogers and this is the bat-fetcher trick with my teeth." There was a whole series of MadTV Kenny Rogers spoofs (see here) but "Kenny Rogers Jackass" tops them all.
"Lorraine Takes Dance Lessons" - Think of Mo Collins' Lorraine Swanson as the cracked out version of SNL's Church Lady.
"Stuart at the Therapist" - "Stuart, what does mamma say?"