Justin Bieber is "gettin better" after collapsing backstage during a London show on Thursday, according to a note the 19-year-old pop star posted to his Instagram account (along with a shirtless pic).

And while his Friday show at The O2 is set to go on as scheduled (the Biebs is just a little "under the weather," a spokeswoman told the AP), he is far from the only celeb to pass out in the middle of a performance. Just last week, One Direction singer Harry Styles collapsed in pain when a fan threw a shoe at his nether regions during a show in Scotland.

SODAHEAD SLIDESHOW: See the scariest onstage collapses.

Last month, goth rocker Marilyn Manson keeled over onstage in Canada while suffering from the flu. And the tradition goes back decades. In 1973, The Who's Keith Moon passed out onstage during "Won't Get Fooled Again" and again during "Magic Bus." Guitarist Pete Townshend famously asked the audience, "Can anyone play the drums? I mean somebody good."

In 2008, Rihanna nearly collapsed onstage during a Sydney performance of "Umbrella" with her now on-again boyfriend Chris Brown. And in 2010, Lady Gaga seemed on the verge of passing out during a performance of "Bad Romance" in New Zealand.

More On This...

PHOTOS: See the latest celebrity pictures to hit the Internet.

From Bieber to Bret Michaels, let us know: Who had the scariest onstage collapse?