As a plot device, crossovers are a time-honored tradition among television series. Whether audiences appreciate these chanced rendezvous is another matter, but two things are certain: several notable encounters exist, and because of them, viewers have witnessed some memorable moments. It's hard to forget such iconic occasions as when the Jetsons met the Flintstones or Adam West's Batman worked with Bruce Lee's Kato from The Green Hornet. What makes meetups like these excellent (regardless of their reception) is that they create a window of opportunity. If done correctly, opening up a series to outside character appearances can be a resourceful avenue for additional writing material and future storylines, and that may be what The Simpsons's writers were going for when they implemented an unexpected crossover with Futurama.
Source：https://www.cbr.com/simpsons-rosebud-mr-burns-appearance-futurama-crossover/
