This Robert Downey Jr./Zach Galifianakis comedy was a miss for the 'Joker' director.

Back in 2010, Robert Downey Jr. and Zach Galifianakis were at the height of their careers thanks to their recent successes in the entertainment industry. 

Downey had quickly become Hollywood's biggest A-list celebrity after he stepped into the role of Marvel's Iron Man, thus kicking off what would become the Marvel Cinematic Universe,

and the entire world was having a love affair with him. Downey had become Hollywood's biggest A-list star after he walked into the position of Marvel's Iron Man.

After that, he was nominated for an Academy Award for his portrayal in the film Tropic Thunder,

and then he went on to star as the legendary investigator Sherlock Holmes. In the meantime, the comic Zach Galifianakis achieved

his long-awaited breakthrough with his performance as Alan in the box office phenomenon The Hangover.

But do you recall when both stars played opposite one another in a buddy comedy about taking a road trip together?

It was a movie from 2010 called "Due Date." Downey and Galifianakis are an unlikely couple in the rambunctious comedy Planes, Trains, and Automobiles, which is kind of a spiritual sequel to the comedy Planes, Trains, and Automobiles, which starred Steve Martin and John Candy.