I'm not sure if anyone had mentioned this but futurama is in the simpsons several times, for example....
1.In one of the couch gags in Season 7, Homer,Marge(who's holding Maggie), and Lisa come through the the tubes(in Futurama) and instead of Bart coming through Fry does.
2.While Homer, Marge, and the kids are renting a video you can see a blury poster that says futurama with fry and bender on it directly behind them.
3.In and episode when the Simpsons look into the future, a older version Homer and Bart drive through a dark tunnel and when they come back through Bender is in the car with them.
4.In one of the episodes a teenager his on a cliff, commiting suicide and with his last words he screams out "Why did you cancil Futurama"
5.In episode where they attend a com-con, where Matt Groening is signing autographs, Milhouse walks up to him with a little bender toy and says "Can you sign my Bender doll"
6.In an episode when the Simpsons get cable, Bart goes nuts in class and all the t.v people apear and one of them is bender.