The character Shawni Burnett was portrayed by Jennifer Lutheran, who appeared in 6 episodes of the HBO Western series, Deadwood, which starred Timothy Olyphant, who portrays Raylan Givens on Justified.
The two hit men are sitting in the car discussing why it's implausible to hold a gun in a moving car and that it was done for dramatic effect and to move the story along. They were talking about a scene in Pulp Fiction (1994) when one character accidentally shoots another in the car resulting in the entrance of Harvey Keitel as Winston Wolfe, the cleaner.
Rollie (Alan Ruck) was inspired to become a dentist when he watched Rudolph the Red-nosed Reindeer (1964) as a child, in which Hermey the Elf wants to be a dentist rather than make toys.