Donald Faison and Zach Braff's bromance is one of Hollywood's most enduring love stories. The "Scrubs" co-stars and real-life BFFS are inseparable -- except when it comes to hitting the gym!

"I would never workout with him ever," Donald told Wonderwall.com of his BFF, who transformed his body in early 2015 after he turned 40 and realized he "wasn't feeling great physically" anymore.

"I don't ever want him to see my workout face," jokes the "Clueless" star.

But what's really behind the (gym) breakup? Apparently Zach -- who served as the best man during Donald's December 2012 wedding to CaCee Cobb and is now their son Rocco's godfather -- isn't afraid to use a little tough love when it comes to motivating his pal to get in shape.

Star Wars Premiere with bae. #blessed

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"He's great at telling me that I'm overweight," Donald told us while launching his "Camp Halftime" video series for the Pepsi Super Bowl 50 Halftime Show.

"The best way to gauge if your friend is a great friend or not is how they tell you you're overweight," he adds. "Zach tells me in the most honest way that I need to lose weight by calling me names like Tubby or Jabba the Hutt -- really nice names that young men need to hear in order to get in shape."

"You want to feel good about yourself? Have your best friend call you Jabba the Hutt. I guarantee you'll jump on the treadmill real quick," continued the 41-year-old father of two.

Why are you in my bathroom?

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Donald lost 30 pounds by boxing two hours every day for a month while preparing for his role in the 2013 film "Kick-Ass 2" but didn't maintain his extreme fitness routine after the action flick wrapped.

"Eating healthy 24/7 is not a goal of mine anymore," he told Wonderwall in early 2013. "I don't think anybody in their right mind should ever do that to yourself."

And so the tables have turned on the long-time friends.

Less booze, more gym.

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Says Donald, "Before, I was the one who was always in shape, so I'd be like, 'Oh, look at the doughnut,' and I'd act like I was using my fingers to make a doughnut around his belly button or a bagel around his bellybutton where you push it together and it looks like a bagel -- and now he can do that to me and I can't say anything because he's walking around in shape."

Fitness may not be a priority for Donald right now, but shaking his groove thing certainly is!

The funny-man will be showing off his moves (sort of) as a choreographer in Pepsi's "Camp Halftime" video series celebrating the unsung heroes of the Super Bowl: the halftime performers who'll be dancing alongside Coldplay and Beyonce on football's biggest night.

"I can dance," Donald says. "Like, if you said, 'Dance on the beat,' I can dance. … You can't tell me I can't keep a beat. I know I got rhythm."

Is that a fact?

Watch the first "Camp Halftime" video below to decide for yourself, and find out more about the Pepsi Super Bowl 50 Halftime Show at Pepsi.com.