This is the fourth episode of the fourth season, and "Thirteen" is its title. One plus three equals four. In numerology, 444 is an angel number. Additionally, in Christianity, there are four Gospels and four Horsemen of the Apocalypse.
Charlie wants to take everyone out to dinner with the first check from his publisher. Don wants to pick the restaurant, thinking Charlie got a big royalty. But Charlie says the check's not *that* big. Charlie's telling the truth, the check he holds up is for $1,396 US. That's equivalent to $2,077 in 2024; not chump change, but not a first-class meal for four in L.A., either.
Guest star Sharif Atkins (Clay Porter) went on to Star in White Collar, on which Diane Farr (Megan Reeves) later guest started in turn. Also, both Sharif Atkins and Dylan Bruno (Colby Granger) later guest starred on SEAL Team.
Thirteen is an unlucky number for many superstitious people in the Western world. This is the fourth episode in the fourth season, and four is an unlucky number for many superstitious people in China.