The flash backer of Keswick (seen in Operation: Happy Birthday) will be in this episode.
In one of the flashbacks will be the father of Dudley and Jim, the Mr.Puppy
In one of the scenes appears the Dudley's hair
An indirect footprints of this episode (in the episode Week of the jokes) can be heard by Dudley, when he says he wanted to be smarter than Jim and he shouts: I HATE YOU, JIM! (yes it seems he forgot that made them). In the same episode (Week of the jokes), there are footprints of Animal Idol.
It's the second episode where the Team Evil (Snaptrap, Bird Brain and the chameleon) has one member absent, in this case is the chameleon, because he remains frozen (more details on The Mansion of Fear), the first episode was Diary of a Mad Cat, where Snaptrap was who was absent.
It will be the second time in the final episode photo Dudley appears with a member of his family, in this case is Jim who pose for photo with Dudley, the first time was in Frisky Bussiness, when Dudley was in the photo the end segment with his mother.