Michael Pena has played everyone from Cesar Chavez to Luis in "Ant-Man" ... but the one role you WON'T see him in is heavyweight boxing champ, Andy Ruiz.
... and why?
"Because I'd have to gain a lot of weight, my wife would kill me!"
Don't get it twisted, Pena has a ton of respect for Ruiz and thinks he has a great story to tell ... but Ruiz is 270 lbs -- and Pena is wayyyyy smaller.
Of course, Ruiz shot to superstardom by knocking out undefeated heavyweight superstar Anthony Joshua -- despite being a HEAVY betting underdog.