Our Special Guest Tonight

That Girl: Marlo meets the Merm.

For some viewers, it's a special treat that makes an otherwise run-of-the-mill sitcom episode stand out. For others, it's a sure sign that the show's writers are fresh out of story ideas. I'm talking about the use of celebrity guest stars in your favorite sitcom.

The idea isn't a new one; radio stars like Jack Benny and Burns and Allen regularly welcomed guest stars at least back to the 1940s. In the mid-1950s, the I Love Lucy writers had the inspired notion to send Lucy, Ricky, and the Mertzes to Hollywood, resulting in unforgettable scenes like Lucy's disastrous meeting with William Holden at the Hollywood Brown Derby, or a classic pantomime with Harpo Marx. Surely no one will ever top Lucy's record for meeting (and annoying!) celebrities in her four weekly series.

Obviously, some shows lend themselves to the concept better than others. Since That Girl told the story of an aspiring actress building a career in New York, it was easy enough to work in guests such as the queen of Broadway musical comedy, Ethel Merman (above). It was a little tougher to logically place Hollywood stars in Hooterville, and you would have thought being stranded on an "uncharted isle" would have kept the cast of Gilligan's Island pretty isolated. That didn't stop Zsa Zsa Gabor, Phil Silvers, and a few others from stopping by, though.

Do you have a favorite sitcom episode featuring a big-name guest star? Feel free to post your choice in the comments below.