"They became really close friends after filming in On the Road," a source close to the pair tells us of the gorgeous actors, whose new flick, based on the famous Jack Kerouac book, is due out later this year.
But despite having worked together, what keeps these two good pals hanging out afterwards?
"They have very similar personalities," our expert insider reveals. "Garrett is a free spirit who is a risk taker, and so is Kristen. Garrett rides a motorcycle, and Kristen is totally into it. They both have a bit of daredevil in them."
Calm down, R.Pattz fans, before sending those death threats to Garrett, you should know that these two buds are strictly platonic. But as long as we've gone there, ya know, should anything ever go wrong with Rob, Garrett sure ain't a bad backup plan for K.Stew!
"They are truly just friends," says our K source, who also adds that Garrett is "currently single."
Last month, the two were spotted partying in London with fellow On the Road costar (and Rob BFF) Tom Sturridge and his ladylove, Sienna Miller. The crew were photographed exiting the Groucho Club in the wee hours of the morning.
And it turns out K.Stew and G.Hed have been spending time together, domestically, too.
"They were hanging out with friends at Chateau Marmont in Los Angeles a few weeks ago," adds the pal of the pair. "They definitely keep in touch."
And while Kris' main man has been sequestered to Canada shooting Cosmopolis, we doubt it's totally painful enjoying the company of a totally hot cowboy in the meantime.
Apparently, Kris just can't resist a dude with a guitar. (We completely understand.)