As a long-time fan of both Doctor Who and MST3K/Rifftrax, I totally did not see this one coming, but now that it's here, it may be the single most important crossover event ever!
Or not. Your mileage may vary.
You can order the riff and movie for already pre-spliced together as a video-on-demand title for $9, here: http://www.rifftrax.com/vod/dr-who-and…. And here's a free sample:
It's been a long time since I watched the Peter Cushing films, mainly because they were roughly 90% retreads of the existing Terry Nation scripts, except with different actors and a completely changed backstory. If both The Daleks and The Dalek Invasion of Earth, had been scrapped along with so many of the other Dalek series from that era, these movies probably would have been remembered a bit more fondly. As it is, they're shiny fluff, which never quite captures the magic of the original, despite the obviously bigger budget.
How will it hold up to a riffing? My guess is not particularly well, but I'll let you know after I've finished downloading it.