Some fans of "Arrow" and "The Flash" may have a difficult time settling on a favorite crossover moment from the two CW series. However, for Stephen Amell, it's an easy choice: "Whenever Diggle interacts with The Flash."

Appearing over the weekend at Salt Lake City Comic Con, Amell and his "Arrow" co-star David Ramsey were asked the question by an audience member, which led to a tease of Diggle's first encounter with Supergirl.

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Ramsey explained that, in an effort to one-up his over-the-top response to the Fastest Man Alive, Diggle would have an involuntary response to meeting Melissa Benoist's Supergirl.

"The thing is now, we're doing our eighth episode is the 100th episode of 'Arrow' [...] So we talked about this with the producers, and it's a big thing," Ramsey explained. "Diggle has to have a reaction to Supergirl, so I decided maybe he could ... pee just a little bit."

"John, she's an alien, she can fly, and she's from a different Earth," Amell deadpanned, before adding, "Did ya pee? A little bit?"

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"Arrow" returns for its fifth season Oct. 5 on The CW, joined Oct. 10 by "Supergirl," which moves to the network from CBS for its second season.