 A clip from " A Clockwork Yellow " was first shown at the San Diego Comic @-@ Con in July 2014 . Executive producer Al Jean spoke to Entertainment Weekly in September 2014 about the third segment of the episode , and the difference in voices between the older and newer versions of the characters . He said that although Dan Castellaneta ’ s portrayal of Homer is better remembered for its evolution over time , Nancy Cartwright ’ s voicing of Bart changed as well , because " it was lower @-@ register , and you can see in the difference in this segment . It was really funny to get the interplay [ between the two versions of the Simpsons ] and for the actors to see the voice evolution . The great thing is we didn ’ t have to ask — we already had the cast hired for the Tracey Ullman Simpsons . " He also revealed that the segment expanded on an earlier episode which implied that the Ullman Simpsons were murdered and buried under the family home , stating " if people want a real Halloween bloodbath , they get it . " 
