Robert Downey, Jr. fell victim to a practical joke on the set of The Avengers sequel when crew members mocked his short stature by replacing his full-size production chair with a miniature version.

The actor reprises his role as superhero Iron Man in upcoming blockbuster The Avengers: Age Of Ultron, and he has risked the wrath of his bosses at Marvel Studios by sharing snaps from the set on his Twitter.com page.

In one shot, Downey, Jr. shows a row of director's-style production chairs stamped with the names of castmembers including Chris Hemsworth, Chris Evans, Mark Ruffalo and Scarlett Johansson.

However, Downey, Jr.'s chair has been swapped with a child-sized version stamped with his name which has been placed in the middle of the row.

The diminutive actor did not seem offended by the swipe at his height and he tweeted the picture to his castmates Evans and Ruffalo with the caption, "Lights, camera, assemble!"

Downey, Jr.'s co-star Ruffalo has also been posting pictures from the set of the film, and his snaps appeared to land him in trouble with producers on Wednesday (23Apr14). He subsequently tweeted, "I'm sorry Marvel. I will be better. I'm like your black sheep Avenger."