Odell Beckham Trades Shots with Shawn Mendes In Rap Battle

Before Odell Beckham hit the gym with Dez Bryant -- he hit the stage with Shawn Mendes for a rap duel on "Drop the Mic" ... and it's pretty great.

The NY Giants star went after Shawn's whiteness ... a lot ... with some lines that included:

"Your skin is so pale, let's call it a hunch ... you're so white, the only meal you eat is brunch."

Also ... "No matter what you say my ego won't burst because whatever you've done, John Mayer did it first."

Mendes came through with some strong shots of his own during the ep which airs Sunday on TBS.

"A dancing athlete that's a little unusual ... its the first time I've seen that since 'High School Musical.'"

And then a short joke ...