Who celebrated First Contact Day yesterday?

Wait, what's First Contact Day, you wonder?

For starters, it's a historic date in future Star Trek history -- in which humans and Vulcans first came into contact with each other on April 5, 2063 -- and to celebrate Star Trek Beyond director Justin Lin has posted this new behind-the-scenes photo of himself with two new alien species... who also happen to be people we know.

Lin teases, "Here I am hanging with two of my favorite people to ever work with. I know this will probably be a tough one since the casting of these two actors hasn’t been announced yet and you won’t find them listed on IMDb. So here’s a hint – I’ve worked with them both before STB. Good luck.”

The photo is also part of a contest where Lin has agreed to toss a Star Trek Beyond crew shirt to the person who correctly guesses the identity of these two aliens (full details here).

So far guesses range from stars of previous Fast & Furious installments, like Vin Diesel, Dwayne Johnson and Sung Kang to comedian Danny Pudi, whom Lin directed in three Community episodes. 

Who do you think is behind the alien masks? Sound off below. Star Trek Beyond hits theaters on July 22.