One of the students in 1985 has a classic Apple t-shirt but in the shape of a banana
Summer is seen having a slumber party with Tricia and Nancy. In previous seasons, Summer hated Tricia for stealing her boyfriend, and had been a friend of Nancy's before blowing her off for being in band.
When snake Adolf Hitler walks through his mansion, a painting of a German shepherd is on the wall, a reference to Its Always Sunny in Philadelphia episode "The Final Solution"
It's mentioned that Rick once trapped Jerry in painting. This is similar to Super Mario 64 and the plot of the quest A Brush With Death featured in The Elder Scrolls IV: Oblivion.