Right after Shawn looks into the snow globe the first time you can see the "Grinch" outside the window behind him stealing a Christmas gift from a couple.
On the show Gus is often mistaken for Bud on The Cosby Show. In this episode, the actress who plays his wife is the same actress who plays Rudy from The Cosby Show.
When Shawn's dreaming and his younger self and super ego are there, they get into a debate about how Young Shawn doesn't look like "us as a kid." Young Shawn says "Well we changed." Up until 2010, Young Shawn was played by Liam James. He was replaced by Skyler Gisondo. This is possibly a reference to that recasting.
When Shawn wakes up in the Blueberry after his second dream, he calls Gus "Kareem." Dule Hill's (Gus) birth name is Karim Dule Hill.
As backup finally arrives, Juliet shouts "what were you guys waiting for-- Canadian Thanksgiving?" Though it's set in Santa Barbara, California, "Psych" is filmed primarily in Vancouver, British Columbia, Canada.