When Mary learns that Mandy's surname is 'McAllister' and therefore of Scottish descent, she asks Mandy "So, you're Catholic?" This supposition is odd since most Christian Scots and Scottish emigrés are Protestant. She may be confused with the Irish, who are more likely to be Catholic.
Sheldon complains that there are no cut-up hot dogs in the spaghetti Brenda Sparks serves. In "The Big Bang Theory" episode "The Spaghetti Catalyst (2010)," it is revealed that Sheldon loved spaghetti that way because that was how his mom served it.
Mandy and Georgie are said to be 29 and 17, respectively. At the time the episode was broadcast, Emily Osment had just turned 30 and Montana Jordan had just turned 19, with their real birth years being 1992 and 2003, respectfully.
At one point in the episode, Sheldon stands outside Missy's bedroom, where she is singing to "Achy Breaky Heart" by Billy Ray Cyrus. Emily Osment (Mandy McAllister) starred alongside Miley Cyrus and her father, Billy Ray Cyrus on the Disney show, Hannah Montana (2006), where they played Lilly Truscott/Lola Luftnagle, Miley Stewart/Hannah Montana and Robby Ray respectively. The song in question came out in 1992.
The episode has Sheldon looking for his Thursday socks, which means the day is April 9th, and three days have passed since the beginning of the last one.