Alice's teeth which were initially covered in blood become clean in between shots.
During the conversation about the "unattached drifter Christmas" the rolled top of the fast-food bag alternates repeatedly from facing the window to facing Sam.
When Sam examines the hearts, the clamps he used to handle the intestines can be seen inside the Tupperware at the beginning, then outside the container on a lid right after the closeup of the heart.
The young man is initially tilting his head to his right before leaning in to kiss his date, but wider camera angles show him leaning to his left without the couple changing their angles during their kisses.
Castiel refers to Cupid as a "cherub, third-class". Cupid is a figure of classical mythology completely unrelated to the cherubim, who are high-ranking angels in the Abrahamic religions (Christian, Jewish and Islamic). Likewise, Dean's description of him as "the little flying fat kid in diapers" refers not to a cherub, which looks like nothing of the sort, but a putto.