With the cast of Avengers: Age of Ultron on tour promoting the movie for the past few weeks, you can only imagine just how exhilarating—but tiring—each day's events must be for them.

That's why it came as a welcome respite when a reporter from MTV asked the cast of the film to play a fun game called "How Well Do the Avengers Know Their Biceps" to find out how well they know each other.

MTV's Josh Horowitz flashed closeup images of the actors' biceps and asked them to identify who the biceps belong to during paired interviews at an Avengers: Age of Ultron press junket.

The first picture Horowitz showed was Chris Evans' (Steve Rogers/Captain America) arm, which Chris Hemsworth (Thor) and Scarlett Johansson (Natasha Romanoff/Black Widow) easily answered.

The second picture got some of the cast a bit confused with. Evans said that it belonged to Hemsworth while Jeremy Renner (Clint Barton/Hawkeye) thought it was Evans' bicep from before he became Captain America. Johansson admitted it was hers, saying that it was "soft and supple."

Horowitz's third picture, a closeup of Robert Downey Jr's (Tony Stark/Iron Man) arm in a scene from Iron Man 2, caught everyone by surprise. Evans, Johansson, and Mark Ruffalo (Bruce Banner/The Hulk) all thought it belonged to Evans, but only Cobie Smulders (Maria Hill) got it right. The musclebound duo of Hemsworth and Evans even joked about not believing it really was Downey's.

Johansson nailed the answer to the fourth picture, a closeup of Hemsworth's bicep, when she said that it was because of the "pointed elbow," which was a frequent topic of conversation among the cast.

She was also the one who got the last picture by recognizing Ruffalo's hairy arms. The rest of the cast also said it was Ruffalo's because of the purple shirt.

Horowitz's interview with the cast of Avengers: Age of Ultron also includes a talk with Johansson and Ruffalo about the rumored budding onscreen romance between the Black Widow and Bruce Banner.

Watch the superheroes flex their muscles against the threat of Ultron in Avengers: Age of Ultron, which opens in theaters on May 1.

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