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During a Tuesday appearance on The Late Show with David Letterman, Hot Pursuit actress Reese Witherspoon had a “blonde moment” when chatting about her 15-year-old lookalike daughter Ava.

When Letterman showed a recent Instagram photo of the two of them that Witherspoon had shared last week, the mom-of-three said, “Actually, coincidentally, she was born the first year I was on this show.”

Joking that he was Ava’s real father (as opposed to Reese’s ex-husband Ryan Phillippe), Letterman responded, “Well, that’s an interesting coincidence.”

While the audience started laughing right away, it took the Academy Award-winning actress, 39, a second to catch on to the quip. “Oh, my God! No, no, no!” she exclaimed once she got the joke.

“I got it now. …I was having a blonde moment,” the Legally Blonde star said. “I have a lot of them lately.”

Chatting again about her daughter, the proud mom said that her gorgeous teen has expressed an interest in acting.

“She’s very artistic though,” Witherspoon said. “She’s sort of a songwriter and she paints. She’s wonderful.”

What about teenage rebellion?

“Not yet,” Witherspoon replied. “No smoking or drinking.”

Witherspoon and Phillippe are also co-parents to a son, Deacon, 11. The actress married talent agent Jim Toth in 2011 and the two are parents to son Tennessee, 2.