POSTED BY STUART LEVINE

First off, I'm a huge champion of "How I Met Your Mother." The cast is terrific, the writing consistently funny and the direction by Pam Fryman is stellar. So speaking from a fan's perspective, last night's episode left me disappointed.

The first time Britney Spears appeared on the show a few weeks back, it was a great piece of stunt casting as showrunners Carter Bays and Craig Thomas integrated her character just enough so that we knew it was Britney but it didn't interfere with how smoothly the rest of the actors work together and it didn't take anything away from the storyline.

Not so much last night. It wasn't that Britney's character -- a young woman who has a crush on Ted but sleeps with Barney to get even -- was involved too much in the episode but, rather, Britney just plain can't act. Period. She looked stilted and foolish in scenes with TV pros such as Neil Patrick Harris and Josh Radnor.

Ratings for "Mother" shot up for Britney's first appearance, and for a show this good that has never received the high ratings it should — series just got the OK from CBS for another season, yeah! — any way to push the Nielsen meter is smart, but last night's episode felt to me as if it had crossed a line in pimping to get viewers.

From Britney's perspective, coming on as a guest star is a smart move. By working on "Mother's" tight sitcom schedule, it helps keep her life straight -- or straighter than usual -- and makes her seem a bit more like a "normal" person and not just tabloid fodder.

But her exposure and rehab felt like it came at the expense of "Mother." I'm hoping it doesn't happen again next season.

It's the bulge that they're all talking about today at MTV. MTV sez that Monday was MTV.com's busiest day ever "by far" with 2.6 million unique visitors, up 40% over its previous record-high, which was day after last year's VMAs.

MTV also reports that it has beamed out more than 7 million video streams of show snippets, a record that beats last year's 6.7 million streams during the same period, and on Sunday night it delivered some 871,000 streams of the full-blown VMA telecast through its MTV Video Music Awards On-Demand service. So while these bulges aren't attached to any of Britney Spears' body parts per se, her much-panned perf helped drive a whole lot 'o this traffic -- undoubtedly more than if the critics had been raving or even lukewarm about her big comeback effort.

Using the old-fashioned Nielsen ratings yardstick, Sunday's live VMA telecast drew an average of 7.1 million viewers, up 23% from last year, when the show's ratings tumbled precipitously. In the MTV target demo of 12-34, kudocast drew 5 million viewers, also up 23% from last year's low ebb.

Meanwhile, David Letterman came up with some face-saving (belly-saving?) excuses for why Britney bombed so badly on Sunday in his Top Ten list on Monday's show. (Click here for the clip.) Among the highlights:

No. 9: I haven't been myself since Phil Rizzuto died.

No. 3: Uh...global warming.

No. 1: Wanted to get myself on Oprah like Dave.

(Pic of Britney Spears by John Shearer/WireImage)