The Bridesmaids actress revealed that she met Jolie and Pitt while walking the red carpet at the Golden Globe Awards last month, an experience which put her in a "weird altered state".
Appearing on The Ellen DeGeneres Show, McCarthy recalled: "So I'm already in some weird altered state talking to Brad and Angelina, They're so nice and chatty and really bubbly. Finally, I got a little weird and I was like, 'You have to stop for a minute because it's a lot visually to take in'.
"They just kind of laughed. I said, 'No really. It is a lot visually to take in'. She's like weirdly glowing. She's so beautiful. He's kind of cute too. And then I was like, 'Okay, I'm sorry'. I needed to regroup because they're kind of a lot."
McCarthy went on to reveal that her embarrassment only increased when she was introduced to Meryl Streep at the same event.
"As I'm talking to them somebody is pulling on my hand and I hear, 'Melissa, Melissa'. And I turned around and she said, 'Hi, I'm Meryl'. Literally, my brain snapped in two. And then I really didn't know what to say. I just kept going 'Oh my God. You're Meryl Streep!' And she was chatting like a normal human being," McCarthy said.
"And I said, 'Oh my god. I'm sorry. I thought over the years so many things if I ever got to meet you... what I would say. This is not it!' And she goes, 'Oh my God. Don't even worry about it'. For some reason I felt I need to bookend it with, and repeat, 'Oh my God. You're Meryl Streep'."
McCarthy has been nominated for an Academy Award in the 'Best Supporting Actress' category for her work in Bridesmaids.
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Watch Melissa McCarthy discuss Angelina Jolie, Brad Pitt and Meryl Streep on The Ellen DeGeneres Show below: