The United States Federal Communications Commission (FCC) "regulates interstate and international communications by radio, television, wire, satellite and cable." Less so than in the years before the internet, they also field complaints from the public about the content on those services. According to the FCC, they use such complaints to "spot trends and practices that warrant investigation and enforcement action." All written complaints older than three years are purged.
A writer for The Atlantic sifted through three years of complaint letters to the FCC focused on the material of Saturday Night Live. Despite the first time it aired being in 2006, one offender was the Justin Timberlake sketch "D*ck in a Box." One viewer wrote,
"It was the Christmas show suggesting that men should give women their penis in a box as a present. I was offended, let alone thinking that younger children would have the opportunity to see the program."
"It was not funny and it was beyond vulgar. The segment even includes Justin Timberlake whom was involved in the Janet Jackson superbowl stunt."
Read more from The Atlantic about things on Saturday Night Live that bothered people enough to write letters of complaint to the FCC here.