22. What significance does this magical number hold for Heidi Montag?

If you guessed that she is about to undergo her 22nd cosmetic surgery... you're probably right. But we're talking about her birthday!

To commemorate this momentous occasion, here's a photo tribute to The Hills star (co-starring her manager and fiance Spencer Pratt, of course). Click to enlarge these Heidi Montag pictures, ranging from all-natural to 100 percent plastic!

Which celebrity birthdays are coming up next? When does your favorite star blow out his or her candles? Follow the link and see!