I have been on a big TMNT kick lately. I grew up with the Turtles and have watched and read every incarnation of them (except for the gonzo anime). I've also been on a Doctor Who kick recently. Why not combine the two?
Okay, I know that initially the two franchises don't seem to have a lot in common. However there have been several times that the Turtles have been featured in space and time based theories. The earliest examples I can think of are the movie Teenage Mutant Ninja Turtles III and the SNES video game Turtles in Time. The movie featured the Turtles being sent back to feudal Japan to save April via a time travel device and the game featured them fighting Shredder and the Foot across various times (past, present, and future). The second (Fox) series also featured the Turtles traveling to various dimensions and alien worlds. It's "sequel" series Teenage Mutant Ninja Turtles Fast Forward even involved the Turtles being sent 100 years into the future. The anniversary special, Turtles Forever, even proposed that each incarnation of TMNT exists in its own dimension.
With all of these alien and time travel stories, why not throw in some Whovian goodness? It may not be for everyone, but I think it would be fun to get some TMNT action and I think Doctor Who: Adventures in Time and Space works just fine as a rules set for it. Well I will throw, in a bit of the action-y goodness of Primeval too.
Also, I'd like to point out that IDW makes Doctor Who and TMNT comics. They've done Doctor Who/ Star Trek crossovers, so a crossover with TMNT isn't totally unthinkable.
My plans are to stat out iconic version of the main characters (possibly with some alternate versions, since characters like Shredder are quite different in a few series). I also want to stat out some of the aliens (Triceratons, Utrom, Krang) and devices/gadgets (like the Time Scepter from the third film). I think it'll be fun.
I'll post the Turtles over the next couple of days and then go on from there.