WATCH: Ed Sheeran's Special Birthday Treat for Bruno Mars

Bruno Mars turned 33 yesterday, and celebrated it backstage before his performance at Bridgestone Arena by "hiring" Ed Sheeran to sing "Happy Birthday" to him -- or so he says on Instagram, where he posted video of Sheeran serenading him while he dug into some birthday cupcakes.

Sheeran also joined Bruno for a duet on the Gingerbread Man's "Thinking Out Loud."



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