I have to be a bit cruel to be kind to you and your question: Kristen Johnston and French Stewart were never the tough ones to get on board. Despite the popularity of the show and its characters, Johnston and Stewart have generally struggled to find work post-"3rd Rock From the Sun." The other half of the show's foursome, however, have thrived: Joseph Gordon-Levitt is now a huge movie star and heartthrob, and John Lithgow's status as a beloved American oddball has only grown with time.

So the fact that Johnston and Stewart now frequently share the screen on the new sitcom "Mom" has only slightly improved the chances of a reunion.

But it is an improvement, if only because it means a reunion on "Mom" would make some sense -- we're already halfway there, numerically at least. Whereas if the other three had, for example, suddenly walked on stage during one of Lithgow's recent Broadway performances, the crowd would have loved it, but they would also have probably said, "Why now?"

And though their schedules are certainly full these days, both Lithgow and Levitt have expressed some willingness to make time for a reunion.

In an informal social media chat back in 2014, Levitt said, "Hell yes … I love all those folks so much, I'd love to."

More recently, Lithgow said on a 2017 episode of "Watch What Happens Live" that he was also interested, but he pointed out that the clock's ticking.

"I would love it. I'm not sure it's doable, though, because Joey Gordon-Levitt has become such a big star, and I've become very old."

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