More than anything, the overall feeling of the dream was that it was a commercial, done in support of some organization, or cause, or something. And I don't recall clearly certain casts being present (really, all I remember were the original cast, and the Next Generation cast), though the idea of the dream was that it was supposed to be everyone. And for some reason Gates McFadden wasn't in pajamas, but a rather simple and basic black bra and panties set. Patrick Stewart was in red silk, Wil Wheaton was in blue flannel (I think with horses on it). William Shatner and Leonard Nimoy were arm in arm, wearing matching pjs, and singing and dancing. They looked like they were having the most fun with it. Brent Spiner was doing the sprinkler, and George Takei started breakdancing at one point. There were a lot of other people there, but the specifics on what they were wearing and how they were dancing are lost in dreamland.
I woke up wishing I could find it on YouTube. I woke up wanting to support whatever it was that they wanted me to. I woke up wanting to ask Wil Wheaton via Twitter if he owned flannel jammies. I woke up feeling good, and smiley, and I giggle a little whenever I think about it. Like I am now, and have been all through the writing of this.