Caitriona Balfe and Sam Heughan's characters have an epic romance on Outlander [1], but off screen, the two have an epic friendship [2]. Case in point: Caitriona's recent birthday messages to Sam. In honour of the Scottish actor's 38th birthday, Caitriona decided to completely troll her costar by posting a number of hilarious photos on Instagram. "Happy Birthday darling!!!" she wrote alongside a photo of Sam photoshopped on her body [3]. "May you feel like a princess alllllll day 😘😘 @SamHeughan 👸🏻👸🏻👸🏼👸🏼." And that's just the icing on the cake . . . pun intended. See the hilarious messages ahead, and then see which other lucky celebrities are part of Sam's inner circle [4].