Cheers, where she sings that theme song before she steps into the world of The Golden Girls with "Thank You for Being a Friend." Next, she sings the Full House theme, and Bob Saget, who starred in the series, appears.
When Saget asks why she's so down, she explains that she's blue because she misses her friends. That's when he guides her to the set of her show and sings the Mary Tyler Moore Show theme "Love Is All Around" to her.