Even if you're not a crossover fan (such as myself), if you spend any time at all on TVtropes, you know that three series
always inevitably cross over with every other series ever created!
Those three series are
Dr. Who,
Warhammer 40,000... and
Magical Girl Lyrical Nanoha.
Edit: For those of you curious or interested, I posted to FF.net the three complete chapters of
Altered Course, the "what-if" AU re-make of MGLN Season One that I started writing some time ago. It's currently on hold, but I'll pick it back up after
false light is done and I'll give Celica a break for a while.