Actor Josh Radnor and guest star Britney Spears(L) in a scene from the CBS comedy series "How I Met Your Mother".(Xinhua/Reuters Photo)

Britney Spears' guest appearance in "How I Met Your Mother" gave the CBS sitcom its highest rating of the season on Monday, and assured the modest performer will be renewed for a fourth season in the fall.

"Mother" pulled in about 10.6 million viewers, a huge spike from its season-to-date average of 7.8 million, according to Nielsen Media Research.

Critics were relatively impressed. "Spears proved she can act every bit as well as she can sing," wrote the New York Daily News. "Brit looked slim, (OK she was behind a desk), trim and gorgeous," wrote the New York Post.

"Mother" was the fourth-highest-rated show of the evening, and CBS won the night (averaging 12.5 million viewers), even as the rest of its comedy lineup dropped slightly from last week's record-setting return to original episodes.

Spears, whose professional achievements have been engulfed by an avalanche of marital, health and legal woes in recent years, played a dermatology office secretary named Abby. She said in a statement issued two weeks ago, while shooting her scenes, that she was having "a blast."

"How I Met Your Mother," narrated through flashbacks from the future, stars Josh Radnor as a man who is joined in his quest for true love by his lecherous pal, played by Neil Patrick Harris.

(Xinhua/Agencies March 26,2008)