In the opening scene in the pharmaceutical lab, there is a sign for Herpexia on the wall. This is the fictional herpes drug Sam was forced to act in a commercial for in the earlier episode, Changing Channels (2009).
One of the sick patients shown waiting in the ER at the beginning of the episode is the store clerk from the end of the previous episode who Pestilence sneezed on.
First time Crowley refers to Sam as "Moose". This would become his nickname of choice for Sam for the remainder of the shows run, and the most frequently used nickname for Sam, unless you count "Sammy".
When Crowley was telling Brady that if Lucifer wins he would kill all the demons he said "when the Morningstar cleans house, we all get the mop." Lucifer's name literally means "bringer of light" (or "bringer of dawn" depending on different texts). In Latin the word "Lucifer" was also used as the name for the morning star, the first star seen in the morning (which is actually the planet Venus). So "Morningstar" became a kind of nickname for Lucifer/Satan.
The Latin incantation that Brady uses to contact Pestilence: "dis manibus praeest praesens obtine mihi dominum pestilentiarum omnium" translates to "of all the present to hold fast to me, is presided over by the lord of the pestilences, the hands of the gods."