Did Reese Witherspoon really have the "best time ever" on Neil Patrick Harris' new show?

The 39-year-old actress looked a little nervous as she agreed to compete with Harris on his NBC program, "Best Time Ever," by climbing up a 15-story contraption and then zip-lining back down.

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Admitting that she was sort of scared of heights, Reese told her longtime pal, "Neil, I am going to bury you."

The former "How I Met Your Mother" star also seemed to be shaken up by the challenge, telling Reese, "That was insane, that was way higher than I thought it would be."

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While the Oscar winner wasn't thrilled about participating in such an extreme sport, she did tell Harris that she'll still be sending his kids, twins Harper and Gideon, Christmas gifts ...but he's off the list!

Reese isn't the only victim of Harris' show shenanigans. The 42-year-old actor revealed to ET that he's also pranking stars, including the judges of "The Voice."

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"I was Jurgen Vulmer, who was the host of 'The Voice' Austria, which doesn't exist," he explained, adding that he basically asked the judges a bunch of strange questions. "I had almost three hours of prosthetic makeup on. I looked nothing like myself, and had a different accent."

"Best Time Ever" airs Tuesday nights on NBC.