Kourtney Kardashian & Travis Barker Power Coupling with MGK & Megan Fox

There was a hot Hollywood quartet out in force this weekend for a UFC event -- which felt like worlds colliding and a generation gap being bridged ... all in a good way, of course.

Kourtney Kardashian and Travis Barker were seated side by side next to none other than Machine Gun Kelly and Megan Fox Saturday night for UFC 260 down in the Vegas area.

The two power couples were seated in their own private booth ... and while a few people behind them had masks on, they all seemed to be relaxing without a worry in the world. The fact guests could even come to this is a sign that ... yes, things are getting back to normal.

Everybody played to the camera when the lens was on them -- MGK and Meg were enjoying their beverages as they flashed different greetings ... while KK and Trav were a bit more on the same page in presenting themselves as a duo. That lollipop choreography was slick!

Seeing all of four of them together is like looking at two sides of the same coin in a way -- the big difference, really, is age. Travis and Kourtney are about 10 or so years older than Kelly and Megan ... but we gotta say, they hold their own with the young bucks, even out in public.