10 Best Doctor Who Crossovers Ever

Time Crash was a short that took place after the events of "Last of the Time Lords. TARDIS spins out of control and sounds an alarm, so the 10th Doctor heads to the control panel to check it out. While he's doing that, he crosses by the 5th Doctor doing the same thing, and the two have a "you're not supposed to be here" moment.

Ultimately, the 10th Doctor inherently knows how to fix the problem that caused their TARDIS' to bring them together. He knows this because he remembered watching himself fix the problem when he was the 5th Doctor. It's all a bunch of wibbly wobbly timey wimey stuff, and it's hilarious.

The short was only a couple of minutes long, but it worked on so many levels. There's more to what's going on in Time Crash than meets the eye, and it has to do with the two actors' relationships to one another.

Most ardent fans know that David Tennant is married to Georgia Tennant. Of course, her maiden name is Moffett, which makes Peter Davison (born Peter Malcolm Gordon Moffett) her father. The scene has two Doctors, the 10th and fifth, but more than that, it's a father-in-law and his son-in-law, which is the perfect sort of absurdity that makes Doctor Who the wonderful series it is.