00:17:35 Spot the pineapple: when Shawn and Gus walk into the Club Restaurant there's a sliced pineapple next to the muffin's plate.
After they visit the environmental watch-dog building, Shawn and Gus banter about "Law and Order". Gus mentions "Milena Govich". Milena Govich had previously guest starred in season 3's, "Earth, Wind and.. Wait for it.." as the fire inspector.
When Gus and Shaun find Mr. Clayton he says something about Waterloo and Shaun says he must be an ABBA fan. Christine Baranski, who played Mrs. Clayton, was in Mamma Mia, a movie musical based on the songs of ABBA. Including Waterloo, which is performed at the end of the movie.
At Clayton's funeral Shawn says "Dust in the wind. All we are is dust in the wind." This is a quote from a Kansas song, Dust in the Wind.
When Nyna asks if they are familiar with Karma, Shawn states that they are "Karma Chameleons", and Gus adds "We come and go". These are lines from Culture Club's song "Karma Chameleon".