This Sunday, “The X-Files” returns to Fox for a limited-engagement series of six episodes. David Duchovny and Gillian Anderson will reprise their roles as Fox Mulder and Dana Scully, parts that made them household names in the 1990s. At one point, it seemed like “The X-Files” was everywhere. Fans became obsessed with the show’s examination of alien encounters and government conspiracies. Another popular Fox show, “The Simpsons,” decided to parody the show early on, but it wasn’t an easy task. Here, “Simpsons” executive producer Al Jean, producer Mike Reiss, animator and consulting producer David Silverman, writer Reid Harrison, and “X-Files” creator Chris Carter look back at “The Springfield Files,” a "Simpsons" series highlight that captured "X-Files" mania at its peak.

The concept for the crossover came to Al Jean at a “Simpsons” writers retreat around 1995.

Al Jean (executive producer, showrunner): We had a retreat where we come prepared with ideas and we pitched them to Jim Brooks. The next morning, we were supposed to attend it. I was trying to think of an idea with Mike Reiss. I walked into the bathroom and there was the TV Guide with “The X-Files” on the cover. I thought “Oh, we should do a crossover.” It’s a good lesson. Read what’s in your bathroom.

Mike Reiss (producer): [The retreats] had become very ritualized. We’d get a nice hotel suite, room service, and we had a gong. Each of the writers would come in with their pitch for an episode. Jim Brooks would discuss it, the staff would kick it around, and if it was approved, we’d hit the gong. It was a very cute ritual. I remember one year we broke the gong. We had to bang an ice bucket. I thought “Wow, this has really gone down hill.” We’re writers and for 10 minutes we had to become pitchmen. There was a lot of pressure.

Al Jean: We thought it would be interesting if there was an alien they were seeing in Springfield. We tried to figure out a plausible explanation for what that alien really was. We pitched it at the retreat but we weren’t the showrunners then. [Mike and I] had a deal at Disney [producing other shows], where they allowed us to do a couple “Simpsons” episodes on the side. So I thought, “I really love this idea, let’s do it.”