Chris Evans has a habit of scaring his costars.

Last year, he spooked Scarlett Johansson during her visit to "The Ellen DeGeneres Show," and now, he's pranking his "Captain America: Civil War" pal, Elizabeth Olsen.

Here's how it went down. Before today's show, the actress was brought to the bathroom by Ellen's staff. "I was told that there were some QVC products in the bathroom to check out. I was like, 'Oh, is that why you did the thing with Julia Roberts the other day?'" she recalls to the audience, sitting next to Evans.

She didn't know that Evans was hiding in the bathroom, waiting to give her the scare of her life. After she saw her hilarious reaction, Olsen laughs and says, "I have a really bad fight or flight response, I think."

But, don't worry, Ellen has her fun with the actor, too!

During a conversation about his dog, Iron Man pops out of the coffee table and freaks out her guest. Check out the clip above to see his funny reaction.

0427-olsen-inset-810x960Launch GalleryGetty"Captain America: Civil War" -- UK Premiere

After all the scares, the costars get to the bottom of those romance rumors. (He was caught checking out her cleavage at the U.K. premiere of "Captain America: Civil War.")

"We've heard that," Evans admits. "Well, we've been dating for like secretly for the last three years," Olsen joke. "We're actually engaged."

The actor jokes that they dated "real on the low" to avoid suspicion. DeGeneres says they "seem compatible," to which Olsen replies, "Maybe we should."

They seem to have a lot of chemistry -- do you think they should date? Sound off in the comment section!

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