NEW YORK (CNN) -- Other than growing a beard that made him look like Rip Van Winkle in a tailored suit, how did David Letterman choose to spend the two months off from his late night show?
David Letterman takes the stage amid a line of chorus girls on Wednesday's "Late Show."
Building a treehouse, he told the giddy studio audience off-camera at the Ed Sullivan Theater.
"Have you ever tried to do that?" he asked the crowd as many chuckled. "I kept dropping the hammer. I spent a lot of time climbing up and down."
As far as jokes go, it wasn't his best, but it didn't seem to matter yesterday.
"I just love him," one woman in a fleece jacket chirped moments before Wednesday's show began. Her boyfriend had just finished proudly licking his show ticket and attaching it to his forehead. "I can't wait to see him. It's been such a long time." Watch the late-night hosts return to work »
The crowd was energized and encouraged to be even more so by Letterman's over-caffeinated staffers. "We seat randomly, so if you have a sour look on your face chances are you could end up in the balcony," said one staffer. He was not kidding.
He then led the audience through a series of exercises, teaching us how to appropriately clap and cheer at the top of our lungs. High pitched woo-hoos don't work. Stay away from the whistles, too. Other than that, he said, "Don't be afraid to really go there." The audience went there -- and so did Letterman.
He appeared to be having a grand old time. Even when he stumbled, he smiled. Being at home didn't suit him at all, he said. It did, however, give him time to "introspect." "Here's what I learned about myself," he said. "Show or no show, I really enjoy drinking in the morning."
He had plenty of time to imbibe. After contract negotiations between the Writers Guild of America and Alliance of Motion Picture and Television Producers stalled in early November, Letterman and his late-night colleagues were immediately forced into repeats.
Along with Letterman, Jay Leno, Conan O'Brien (also sporting facial hair), Craig Ferguson and Jimmy Kimmel returned to work yesterday. Thanks to a separate agreement reached Friday between Letterman's production company, Worldwide Pants, and the guild, the host was able to return to work with his staff writers. Leno, O'Brien and Kimmel had to go at it alone.
The show began with good cheer. The high-kicking chorus girls carrying pickets signs were cute and the "Top 10 List" clever (No. 10: "A complimentary tote bag with next insulting contract offer"). Even Letterman's attempt to explain what the strike is really about -- "pencils, this is all about pencils" -- went over well.
The host's woolly facial hair only added to the spectacle -- and provided loads of joke fodder. As soon as the ever-manic Robin Williams bounded on stage, he pulled out his verbal Tommy gun and sprayed Letterman with insults.
"Ladies and gentleman, here is General Lee. Before we begin our Civil War reenactment ..." The crowd liked that one. In an obvious reference to Abraham Lincoln, Williams joked, "Be careful, someone may try and assassinate you." They liked that one too.
Letterman's show did produce some yawn-inducing moments -- Dave, please cut the interviews with your show's behind-the-scenes players -- and the pro-writer rhetoric did eventually grow a little heavy-handed.
Nevertheless, his fans cut Letterman some slack.
"Dave totally rocked," one young man exclaimed as he strode out the doors smiling. E-mail to a friend