Zach Galifianakis underwent a temporary role reversal after spotting his "Due Date" co-star Robert Downey Jr. on a Comic-Con press line over the weekend.

"Is it a lot of work to do a movie?" he asked, sneaking up from behind Downey with a borrowed microphone in hand. "What kind of pranks do you do on set?"

After a brief reunion that saw the two embrace while surrounded by an army of reporters, Galifianakis scurried off to continue promoting his upcoming comedy "The Campaign" further down the carpet. Oh, tender moments!

After checking out video of the poignant reunion above, be sure and click on over to our complete press line interviews with Downey Jr. (here) and Galifianakis, the latter of whom gave me $20!

"Due Date" grossed over $200 million worldwide.

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