Looks like there are alot of new users here who don't realize reddit has historically had alot of users who really like the daily show and colbert report, and colbert has mentioned being a redditor before.

Its not the first time he's mentioned reddit, this is from September 7th 2010: http://www.reddit.com/r/reddit.com/comments/daxgp/queue_stephen_colbert_just_mentioned_reddit_spam/ was one of many posts about it. Was mentioned in an interview about how he can go on the site and spend hours on it, in one of his out of character moments. Which is how reddit realized we could "get messages" to Steven if we got it on the front page, which you still see from time to time like why SOPA wasn't being addressed on the shows. Eventually after him first mentioning it, this lead to the posting of the satirical rally idea someone had eventually, to mock the tea party at the time, which got to the front page big time. Then reddit also got someone to ask Stewart about it during the Q&A before the show. Reddit Then Donated $200k to donors choose charity - Colbert is on the board of directors - to convince them (Colbert and Stewart) to do the rally. They already had been throwing the idea around about a rally they claimed although was never mentioned publically, but reddit probably helped give them the ability to do it by showing a huge amount of support for the idea.

And after Donors Choose he did this: http://www.reddit.com/r/reddit.com/comments/e0f4k/stephen_colbert_just_drew_the_reddit_alien_on_the/ A pretty sly shout out by drawing a reddit alien on the back of the blue sheets they have on their desk and coming back from commercial shuffled them to show the reddit alien for a good few seconds.

Finally, 4-5 years ago reddit had full episodes of the daily show and colbert report back when youtube allowed such stuff. Actually since google acquired youtube they were sued and google won(?) or at least proved in their lawsuit that Viacom was uploading some of it to promote the show giving them a huge legal win.