Dave on Demand: A crackling, cameo-studded "30 Rock" celebration

Have you ever noticed, when it's time for TV to amp up its game for a special occasion, it usually chokes?

Take, for example, series finales from Seinfeld to The Sopranos. Or the feeble way American Idol said goodbye to Simon Cowell last year after nine seasons.

But 30 Rock did not disappoint Thursday night, coming up big with a crackling hour-long program to celebrate its 100th episode.

There were barbs directed at everyone from Nate Berkus to John Stossel.

The slate of guest appearances was remarkable: Rachael Ray, Rachel Dratch, Regis and Kelly, Matt Lauer, Michael Keaton, a Bono look-alike, and the topper: Tom Hanks doing needlepoint while singing the bad Billy Joel song "My Life," which just happened to be the theme song from Hanks' embarrassing '80s sitcom, Bosom Buddies (jokes within jokes!).

The episode marked the return of Liz's epically bad boyfriend, Denny (Dean Winters, now maybe better known as the accident-causing "Mayhem" in the Allstate commercials).

Even the throwaway lines were funny, as when Denny mentioned that he went to Gerry Cooney Elementary School.

How about when Dr. Spaceman checked out Pete to see if he had recovered from the gas leak? He asked him to recite the alphabet, and Pete delivered a syllable-by-syllable re-creation of the gibberish spouted by that L.A. TV reporter at the Grammys.

30 Rock matadored NBC's new owner, Kabletown. In case you weren't aware they were spoofing Comcast, the show began with Jack knotting up a Flyers tie to impress his new boss, Hank (a perfectly unhinged Ken Howard).

Taking Liz in bear-hug, the Kabletown exec said, "I know a Philly girl when I hug one."

After visiting NBC News' studio, Hank observed with alarm, "Brian Williams sure gets close to you when he talks. Very feminine energy."

There was a Scrooge-like subplot, with four Jacks. (Good poker hand, no?) Did you notice how the slicked-back hair of Sideways Jack made Alec Baldwin look like his brother Daniel?

I would rank this, along with the 30 Rock's "Queen of Jordan" Real Housewives satire, among the best sitcom episodes of all time. That's two instant classics in one season. Well-played, 30 Rock, well-played.

Never was heard a discouraging word. The American Idol judges can't help it if they're more upbeat than Richard Simmons.

This week, they tried, they really did, to stop crushing on the contestants long enough to deliver some actual critiques of their singing.

That stab at objectivity lasted one song. Then James Durbin performed "Uprising," and Steven, Jennifer, and Randy began exalting it, practically in unison, as "the best performance of the night!"

Umm, guys, you might want to hold off until the other five singers have had a chance. It was reminiscent of the time on Idol when Paula Abdul assessed Jason Castro's second song in some detail - before he sang it.

That fish looks suspicious. All week long, Entertainment Tonight has been going at the Royal Wedding hammer and tongs. The show seems particularly obsessed with the ceremony's security measures.

Jane Seymour, a member of ET's Royal Wedding team (really, they have one), speculated that there might even be frogmen patrolling the Thames. Seymour reported that Scotland Yard spokesmen would not confirm this possibility. Maybe because they couldn't stop laughing.

Aloha. Worst performance of the week: the guest appearance of Sean Combs (a.k.a. Diddy) on Hawaii Five-O.

He played a guy who had infiltrated the mob for the FBI. Combs wore the same expression through the entire episode, even when he took two slugs in the stomach. Now, that's stoic.

A danger to democracy. Conan O'Brien uncorked a winner about fired Celebrity Apprentice contestant Gary Busey. "In an interview for the Today show," Conan quipped, "Gary Busey said that Donald Trump would be an 'absolutely good president.' Busey said, 'Trump knows how to stand up to our enemies, Iran, North Korea, and Meat Loaf.' "