Taking Back Sunday Rocker -- My Birthday Stripper ... Has a Penis!

The guitar player from Taking Back Sunday was super stoked when he found out his bandmates got him a stripper for his birthday ... and then he realized, it was a dude.

It all went down on stage at a concert in Providence, Rhode Island on Tuesday night ... when the band behind the hit "MakeDamnSure" surprised Eddie Reyes with a live strip show.

Long story short ... stripper turned out to be a guy. He stripped down to his undies. He's hot ... and Eddie handled the whole thing like a champ.