There's a lot of really grand conceits in fandom, not the least of which is the urge to combine SF universes that don't have any connection with each other. It's a staple of fanfic - the TOS Enterprise meets Moonbase Alpha, or Dr. Who meets the (original) Galactica, or the Jupiter II visits The Seaview, or Quantum Leap bumps into Time Tunnel, or Kolchack turns up alongside Mulder and Scully. It's fun, it kind of writes itself, and of course you're not limited by copyright, budget, or the death of actors.