Not exactly a crossover in the truest sense, but I was shocked that Tom Selleck never reprised his role of Magnum on Jag. Seems like it was the perfect opportunity to have seen the "big guy" one more time.
I always wanted to see the Quantum Leap/Magnum
crossover, where all of the Magnum actors would have reprised their roles. From what I've always understood, it would have happened if Quantum
had had another season.