The food trucks are parked in front of Bazzo's, a throwback to We'd Like to Thank the Academy (2010).
While in the interrogation room, Shawn mentions the movie Holes (2003). Actor Dulé Hill, who plays Gus, was in "Holes".
Shawn mentions that Lassiter's practice baby has "Brad Dourif hair". Brad Dourif is the actor who played Bernie Bethel in Shawn Interrupted (2011) and has been open about having hair restoration. Dourif is known for playing eccentric and psychotic characters.
The film constantly being referenced ("Is that [blank] in there? Is that [blank] in there?!") is Mystic River (2003), specifically Sean Penn's line, "Is that my daughter in there? Is that my daughter in there?!".
When Shawn & Gus are talking to Frank, he says that a lot of food trucks close and mentions "Pizza In A Cup" closed down. This is a reference to the film The Jerk (1979) in which Steve Martin & Bernadette Peters characters are eating food from the fictional restaurant "Pizza In A Cup."