Sofia, Joe & Arnold Random NYE Date Night Dinner and a ... Britney Concert

1/1/2015 7:35 AM PST

Sofia Vergara, Joe Manganiello & Arnold Schwarzenegger -- Random NYE Date Night ... Dinner and a Britney Spears Concert

Random thing 1: Sofia Vergara, Joe Manganiello and Arnold Schwarzenegger all hung out together on New Year's Eve. Random thing 2: They went took in a Britney Spears performance!

We're on the fence about which thing is more random -- but yeah, the 3 celebs and Arnold's gf Heather Milligan ... hit up Planet Hollywood in Las Vegas for a steak dinner, and Britney's "Piece of Me" show.

Sofia still managed to keep that engagement ring (rumored to be 10 carats) under wraps -- just like she did in Hawaii right after Joe gave it to her. 

What's impossible to hide is -- this is the most ridiculously fit double date ever. Joe and Ahnald at the same table? That's a ton o' tickets to the gun show, son.