Shawn: Abigail Lytar. Judd Nelson.
This is a reference to episode 2 of this season, Murder?...Anyone?...Anyone?...Bueller?, in which Gus insists instead of name tags, everyone wear their graduation photo. Instead of his own, Shawn wears a picture of Judd Nelson. When he sees Abigail she greets him as Judd Nelson.
Shawn: I’ll pick you up at seven. I’ll be the one flaring my nostrils uncontrollably.
This is another reference to Murder?...Anyone?...Anyone?...Bueller?, when Shawn implies he believes Judd Nelson flared his nostrils too much in From the Hip.
Visual: The photograph of Shawn that Mr Yang uses to single him out to play her game.
This is the same image seen in the museum in Shawn (and Gus) of the Dead to dedicate the discovery of the T-Rex skull to Shawn.
Visual: The newspaper lining the mouse cage has two personal ads, with plays on Shawn’s previous cases: ’Adam Hornstock selling black snake, will go fast,’ and ‘Mira Gaffney seeks Bruton Gaster to love her tender.’
Adam Hornstock was the lawyer from Cloudy... With a Chance of Murder that Shawn and Gus helped out.
Mira Gaffney is Gus’s ex-wife from There’s Something About Mira.
Bruton Gaster is the misspelling of Gus’s name from the plaque in the museum, which Shawn also uses as an alias at the end of Shawn (and Gus) of the Dead.
Mary: Finding Bouchard's treasure was extremely impressive.
Mary is referring to Shawn and Gus uncovering lost treasure in The Greatest Adventure in the History of Basic Cable.
Juliet: You can count me in for next year’s re-enactment, partner!
In season 1 episode, Weekend Warriors, Lassiter is seen to be in charge of an annual Civil War re-enactment.
Gus: Brendan Vu! From the Spelling Bee!
Trying to figure out why Yang spelt the word view ‘vu’ Gus guesses that maybe she’s referencing their case from season one episode two, Spellingg Bee. Brendan Vu was the victim that lead Shawn and Gus to take the case.