Coco’s going out on top.

Thursday’s penultimate edition of "The Tonight Show With Conan O’Brien," which featured visits from Robin Williams, Ben Stiller and Pee-wee Herman, exploded to a 2.6 rating among adults 18-49. That’s nearly double the average for primetime’s "The Jay Leno Show" (1.4) and essentially triple the tune-in for "Late Show With David Lenohater" (0.9).

It’s also, by far, the best tune-in for Conan since The Troubles began, and 30 percent better than Wednesday’s show. Plus, it’s a larger young adult average than Jay and Dave combined. (Ratings are overnight numbers from Nielsen’s 25 metered markets with demo data available. Final numbers out next week).

So much for Nielsen guru Jay Leno’s maxim, "When you don’t get the ratings, they take you off the air."

The Coco imbroglio (good one, right?) is also proving to be quite a goodbye gift from O’Brien to his "Late Night" successor, Jimmy Fallon. Thursday’s Fallon notched a 1.0 in the demo, better than Letterman and Jimmy Kimmel (0.5),who air in earlier timeslots.

While it would be logical to think O’Brien should do even better in the Nielsens with tonight’s exit, don’t forget that audience levels drop dramatically from Thursday to Friday in primetime — and we live in the DVR era. O’Brien might still climb again in the ratings, but don’t be shocked if he’s hit a ceiling.

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