Add another dimension to Marcus Smart's complex personality.

The 25-year-old guard, one of four Boston Celtics players on Team USA, is viewed as a leader for the Americans entering the 2019 FIBA World Cup.

He's also getting along very well with his USA teammates -- to the point where he's been dubbed Brooklyn Nets wing Joe Harris' "alter ego."

The Athletic's Joe Vardon explained in a column Friday: Smart, the "feisty, rugged Boston spark plug from Flower Mound, Texas" is the perfect foil to Harris, "the white, bearded, semi-preppy, quasi-hipster 3-point shooter from Chelan, Wash.," so both players are taking the joke and running with it.

"You've got anything to say about Joe, you say it to me because I'm his alter ego," Smart told Vardon. "He's always telling me I'm his alter ego. The things he won't do or say, I do it for him. It's kind of funny."

Harris apparently has riffed on this bit in group text threads, telling his teammates, "All business inquiries, see Marcus. Anything you've got going on, see Marcus."

Smart fits that role well as Harris' wild-card, loose cannon alter ego. (He's not quite Tyler Durden in Fight Club, but you get the idea.)

More importantly, Smart and his fellow "Team Shamrock" members -- Kemba Walker, Jayson Tatum and Jaylen Brown -- are integrating seamlessly overseas, with players and officials telling Vardon the whole squad is more close-knit than in years past.

The Celtics are hoping their quartet brings that chemistry back to Boston -- and that Smart doesn't get Harris in trouble over the next two weeks.

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Team USA hilariously brands Marcus Smart as Joe Harris' 'alter ego' originally appeared on NBC Sports Boston