So I gather that from an audience perspective, that was pretty funny. But was anybody thinking about the snail?
I am 95% sure that "Megyn Shelly," the brunt of the hilarity in Mr. Colbert's cruel prank, was a young adult Pomacea bridgesii  - the South American ampullariid that has risen to such popularity with aquarium hobbyists in recent years. I believe that's the variant with the albino body but pigmented shell .
So of course "Megyn" could not move when placed under the heat of Mr. Colbert's swirling spotlights - freshwater gastropods are notoriously immobile when suddenly transported into the terrestrial environment. In fact, she was holding her breath, fearing for her life. As Colbert and his heartless audience mocked and scorned! How could such a travesty be perpetrated?
I would speculate that Mr. Colbert suffers from a dearth of malacological expertise in his staff of comedy writers. So my guess would be, judging from the podia, that the part of Megyn Shelly was originally written for a land snail. And that only after plans were made, and cucumbers assembled, was some young intern tasked to call the local pet shops and audition a star for the show. On a short time line.
But I am not sure, even in New York City, that one can find a living land snail for pickup on short notice. Those things are pretty much all potential agricultural pests, every one of them, and the interest in the pet trade must be very close to negligible. One might order Helix aspersa from a biological supply company, but such an approach would have been no help to our young intern, who needed a star for the show that very evening.
So the talent agent at the pet shop on the other end of the telephone might well have responded to her renewed entreaties, "We've got some decent-sized aquarium snails we could sell you this afternoon." And by such a scenario, victimized by malacological fashion, USDA regulation, and cruel fate, I should speculate that our luckless ampullariid found herself dewatered on national television, to the general hilarity.
I know you read this blog, Colbert, and I have a prophecy for you. At the present writing (February 3) only four candidates remain in the running for the Republican presidential nomination. You endorsed Herman Cain right here on the CofC campus January 20, but Herman Cain endorsed Newt Gingrich eight days later. I predict this wave will carry Newt Gingrich to a victory in November.
A Gingrich presidency will cast a shadow over your rich, liberal, New York media establishment no different from the darkest hour of the McCarthy Era, Colbert! Megyn may have seen her low-water mark on your television show that fateful night of January 3. But you have seen your high.
 The clip can be viewed in a slightly larger format back at the Comedy Central mother ship here [Comedy Central].
 Is the common aquarium pet now being referred to P. diffusa? I saw an oral presentation from Ken Hayes at the AMS in July that suggested a huge amount of revision on the horizon for the Ampullariidae, including yet another name change for the invasive populations we're now calling P. insularum. But I haven't seen anything published since 2007. Have I missed a paper? Ken or Rob, would you care to enlighten us?
 There's a very nice website dedicated to apple snails in the aquarium run by a dedicated hobbyist named Stijn Ghesquiere here [applesnail.net]. The site features a cute (and credible) "hypothesis" regarding the genetic basis of the various color forms seen in P. bridgesii. But I do wish somebody would undertake a good, old-fashioned, Mendelian breeding study! And publish something formal.