Mark Cuban -- Warren Buffett Is My Homeboy (Video)

Mark Cuban and Warren Buffett are more than just billionaire "Entourage" co-stars ... they're also friends in real life who get ICE CREAM together.

Cuban just appeared on "TMZ Hollywood Sports" to talk about his cameo in the upcoming flick -- we asked if he and Buffett got along on the set since they have so much in common.

That's when Cuban told us ... he flew out to Buffett's hood just yesterday for a business lunch that was capped off with dessert at Dairy Queen ... which is owned by Buffett.

Question is ... who pays when two billionaires get dessert??? Check out the clip.

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