Robert Downey, Jr. proved he is still young at heart by spending his 49th birthday with 20 kids at a special screening of new Marvel movie Captain America: The Winter Soldier.

The Iron Man star turned a year older on Friday (04Apr14) and decided to spend his birthday at a film with a huge group of children.

He took to Facebook.com to post a snap of himself at the screening, alongside the caption, "What better way to spend my birthday than recognizing the cosmic miracle of Captain America 2 opening the same day?

"Gonna wrangle about twenty kids to watch it with and partaaaaaaaaaaaaay Marvel-style!!! Let the partaaaaay begin!!!"

Last year (13), the star joined the Guinness World Record books on his 48th birthday when he was handed a huge card with more 5,000 signatures during a promotional trip to Beijing, China.