We can't blame actors for dating each other, but we can blame them for breaking our hearts in the process. As if those "love at first sight" plots don't trample our inner-teenager's fantasies enough, some TV and movie co-stars have taken our heartbreak to unforgivable levels by dating each other off-screen.

Okay, okay, Freddie Prinze Jr. and Sarah Michelle Gellar (still) look pretty damn good together in the years since they met on the set of I Know What You Did Last Summer. And Ryan Gosling and Eva Mendes' still-unrevealed-but-inevitably-cute daughters would never be, had the couple not gotten together while filming A Place Beyond the Pines.

And those are just two instances in which celebs have found themselves smitten with their co-stars — check out the gallery above to see which other celebrity cast mates caught a case of the love bug on set.