Arrow star Stephen Amell debuted a new super costume this weekend: The actor stripped down to a pair of camouflage briefs at co-star John Barrowman's 50th birthday.

"Here’s the thing—John Barrowman is only turning 50 once," Amell explained on Instagram. He and another friend in undies sported Barrowman's initials on their bare chest.

On social media, the birthday boy posted a shot and called it "one of my favorite pictures from my birthday party." (We don't think he meant the cake, though that looks lovely, too.)

Barrowman, who shaved his hair down to its natural gray roots, also debuted a t-shirt supporting transgender equality.

You can order one here.

Below, more birthday love for Barrowman

h/t: Gay Star News