Watch: New and Original 'Ghostbusters' Casts Unite

As promised, the new and original casts of "Ghostbusters" united Wednesday on "Jimmy Kimmel Live," delivering pretty much everything a franchise fan might want -- well, except for Sigourney Weaver and Chris Hemsworth. There was laughing, there was signing, there was dancing -- oh, was there dancing.

Seriously, most fans probably would've been happy with an hour of Bill Murray gettin' down as Ray Parker Jr. performed the "Ghostbusters" theme.

However, there was much more than that, as Murray and fellow original cast members Dan Aykroyd, Ernie Hudson and Annie Potts joined franchise newcomers Melissa McCarthy, Kristen Wiig, Leslie Jones and Kate McKinnon for a sitdown with Kimmel.

Aside from bouncing up and down with Wiig, Murray used the opportunity to explain what led to his involvement in Paul Feig's remake after resisting so many proposed "Ghostbusters" projects.

"It was only 'cause I knew these girls were funny," he said, adding. "When you see the film, and you'll delight in the film, it sort of rumbles along in the beginning, and you're going, 'Oh, God, are they gonna pull this thing off?' No, really, I feel like a stepfather to the whole thing ... There is just no quit in these girls. [...] This is a tough movie to pull off, 'cause it's a big concept, there's a lot on the plate, and there's a lot of expectation, but Danny and I, and Annie and Ernie, were just screaming, cheering like we were at a sporting event at the end of it."

"Ghostbusters" opens July 15.

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