Shay Mitchell’s birthday party photo is the gift that keeps on giving! The actress’ party was attended by many of her Pretty Little Liars co-stars, including both Ian Harding (Ezra) and Troian Bellisario (Spencer). Both Ian and Troian are sitting right in front for the “family photo” taken at the end of the night, and one of their expressions is slightly sillier than the other’s.

“Troian was supposed to join me in "stupid face" #leftmehangin,” Ian tweeted yesterday, obviously appalled that his friend and co-star left him in the lurch. In the photo, Ian and Troian are sitting on a bench in the very front, their hands adorably together on Troian’s lap, but that’s apparently where their unity ends. While Troin has the sweetest of smiles on her face, Ian is doing his best Goofy Schuck Face for the camera. Oh, how we love this picture.

This isn’t the first time Ian has expressed his frustration with Troian regarding a photo over social media. Last year, Troian provoked Ian by tweeting a photo of she and co-star Brandon W. Jones in front of the chalkboard in Ezra’s classroom. Written on the chalkboard: “Mr. Fitz sucks.” Ha! “Just because we're the smartest kids in school doesn't mean we're not badass. @Brandonwjones and I say Suck it @actuallyharding,” Troian awesomely tweeted at Ian.

Ian fired back: “@SleepintheGardn nice Instagram post ya douche,” along with the teasing threat: “oh hahahahahhaha ha wow that's so great DON'T SLEEP TONIGHT.”

And we still laugh whenever we think of the all-cast teasing of Ian on Twitter over the hilarious Sheetz Smoothie advertisement he filmed in his earlier years. We’re beginning to think that Ian may just be one of those people who it’s impossible to resist teasing -- and we only love him for it!

Catch the next episode of Pretty Little Liars on June 10, 2014 at 8 p.m. ET on ABC.

Kayti Burt is a contributing writer for Wetpaint Entertainment with a penchant for all things pop culture. Follow her on Twitter and Google+!