Robert Downey Jr. just released an image of himself on Instagram seemingly to help promote a friend's endeavor as well as to tease fans with his upcoming role in "Avengers: Doomsday".

Robert Downey Jr.'s latest behind-the-scene tease for Avengers: Doomsday suggests a fan-favorite superhero team could join ...

Instead, Downey Jr. will debut as the iconic Marvel supervillain Doctor Doom, with the actor having now teased his MCU comeback in a new image from the set of the Avengers sequel.