The joke would have happened during the back and forth when Tony and Strange interact in the park while Stark and Pepper are walking.

"I should've said, 'No shit, Sherlock,'" one of the Russo brothers noted of the moment on the Infinity War commentary track. "Everybody really wanted that joke."

Cumberbatch has starred as Sherlock Holmes on the popular BBC series Sherlock since 2010. Downey has played the detective in two Guy Ritchie movies, released in 2009 and 2011.

"It's a meta joke that requires you to be a fan of other movies," the other Russo brother said.

The first Russo followed up quickly, "It is also a very obvious joke. Not that we can't be accused of having made obvious jokes before."

Avengers: Infinity War is available digitally now and on Blu-ray Aug. 14.