When Letterman announced that tonight’s “Late Show” would include Julianne Moore plus Morgan Spurlock plus the winner of the National Spelling Bee plus a performance by the cast of “South Pacific,” I thought, “well, that’s a pretty full show. No room for anything else.”

But about 15 minutes in, I was proven wrong. Some city slicker did a walk-on to promote the release of a new DVD edition of one of his most popular movies.

I love the way that Paul Shaffer sometimes plays “Thanks for the Memories” to accompany such surprise walk-ons, a joking reference to the days when Bob Hope would be taping one of his NBC specials and would turn up on the Carson show unannounced.

UPDATE: The announced guest list turned out to be a red herring: the spelling bee winner wasn’t the real spelling bee winner but a thirty-something actor doing a comedy bit.