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Howie Mandel is already BFFs with Heidi Klum -- his new fellow judge on "America's Got Talent" -- in fact, the two are on such close terms ... Howie has no problem cracking jokes about Heidi slapping her estranged husband Seal.
Howie called in to TMZ Live today to talk about Heidi ... and before we knew it, she jumped on the phone to tell us how excited she was to be on the show, saying, "I'm about to hit the 'X'!"
We won't give away Howie's retort ... but you can probably guess where it's heading ... and it's hilarious. You gotta watch the clip.
TMZ broke the story ... Heidi will be one of the new judges on "AGT" alongside Howie, Howard Stern, and Mel B.