A Player's Guide to Canon Puncturing
It's taken me a while to figure out how I want to handle this, but after playing around with canon a bit, I've sort of come to a solution that I think works rather nicely.
Right now, as is mentioned in his bio post, it's currently 1987 on Teller's timeline. Since this is a bizarro-world AU version, where aliens and monsters exist, a few key details are different. For one, he and Penn have not started touring yet. As of this post, they've just made their first TV appearance. This is considerably different from the actual time line.
Furthermore, his millicanon will be made very meta. 90% of it is (as of right now) from the Invisible Thread canon. In this film, he's a nobody shop owner who occasionally does small shows at parties and the like.
However, recently, they caught the attention of a talent scout, and now they're sort of treading into the beginning of Get Killed territory (which will likely lead to a full-on brand new AU continuity after about the first 15 minutes of the film). In Get Killed, clips of Invisible Thread are shown on a television set, which means that actually, they are two different continuities and time lines. Anything that happened in the real world continuity/lore (things that they claim happened, but no real proof exists) that I choose to include will be skewed slightly, to be just on this side of recognisable. For instance, they're not appearing on SNL, but rather some other generic Friday night comedy programme (on NBC).
HOWEVER, I have decided to combine bits and pieces, since I'm allowed to do that. This means that the duo known as Penn & Teller will gain some level of fame (or, as the case may be, infamy) in their own universe. By all means, if your character would be familiar with their brand of frightening magic, go ahead and recognise Teller.
He's a smart chap, and he's very quickly figured out that time does not work in a normal way at Milliways, so if he thinks you may be about to reveal "spoilers," he will stop you. He won't know at all what you're talking about if you mention any of the films, specials, or billions guest appearances they've made over the years, even if they would have already happened on his time line. Mainly because, as mentioned above, they didn't happen, or if they did, it was under different circumstances (and, in fact, I'd rather prefer it if the films were just ignored, entirely. For now, anyway).
Also, just because it amuses me, part of the lore that is included in his time line also involves the Cryptic Corporation. He will occasionally be in the bar wearing a Residents Eyeball t-shirt, and has even implied that they are not from this planet. I'm not going to explain here why this is hilarious, but if you're really curious, feel free to ping me on AIM.
For further explanation of "different circumstances," see this post.
TL;DR, feel free to recognise him as a performer, but don't be surprised if he gives you a very confused look.