Calling it “the most passionate moment I have heard about Star Trek,” Shatner explained that the driver told him that the series helped soldiers during the Vietnam War.

“He wanted to tell me a story, and as he began to tell me, tears started coursing down his cheeks,” Shatner told Rivers. “He said that he had been in Vietnam and had been captured. And that a group of his friends who had been in the same cell — the only way that they could keep themselves alive was to play the Star Trek game.”

Shatner said he wasn’t sure what the veteran meant, so he asked to know more.

“These were episodes that these young soldiers had memorized over the years — and in some cases, they were strangers to each other — but they knew the plots and the dialogue and they would repeat the dialogue to each other and play an hour’s segment to each other of Star Trek. And in that manner, they kept themselves not only alive, but sane. And it was the most moving story of that kind that I’ve ever heard.”

Rivers quickly interjected a joke at the end. "Did you tip him or did you think he got enough out of you already?" she quipped.

Shatner played Capt. Kirk on three seasons of the original TV series and in seven feature films. He most recently guest-starred on The Big Bang Theory.