The Friday Night Line-Up is a series of shows that airs every Friday Night in the Boy Meets World universe. One of the shows on it featured a trouble-prone, curly haired kid. (The show was a personal favorite of Billy Epperson.) The show was inexplicably moved from 8:30 to 9:30, causing outrage from Billy and Cory.
The Friday Night Line-Up is a clear parody off of TGIF, and the issue with Billy's favorite show switching timeslots is a reference to Boy Meets World also switching timeslots (from 8:30 to 9:30), which dismayed the show's creators and fans.