There is a rich history of crossovers in film. As early as 1943 their was a crossover of horror greats in Frankenstein Meets Wolf Man, but it took a while for the tradition to make it to the small screen.
Famously, in 1990 an East German and West German mystery series had a crossover in which their respective detectives investigate a crime taking place just after the fall of the Berlin Wall, and since then we have seen more and more TV crossovers.
There are many reasons a show can decide to do a crossover: fan service, ratings, wanting to tell a story that combines two different worlds and characters, or merely a network wanting to introduce one show to a different show's audience.
It's always fascinating to see how a crossover navigates bringing two shows together, sometimes with a delicate balance that keeps the integrity of both worlds, sometimes with the wild abandon of a drunk clown throwing hammers at a nail.
Here are ten of the wildest, weirdest and sometimes wonderful crossovers from TV shows we love.