The capture came from a site known to fabricate stuff and there is no sign of the original post. Probably photoshopped.
I wouldn't be surprised if they went to a movie or something though, 2PM and SNSD have mentioned going to concerts together and out to eat and what not.
People throw stuff out there all the time. This sounds like just a classic case of trying to bring credibility to something by making a vague connection to another thing that's hot at the moment. The "I work at a karaoke box and saw this" or "I work at a theater and saw that" are like the oldest trick in the book.