Actor Allusion: After Karma lists all the qualities that make Liam so dreamy, Amy replies, "You said that about Ryan Seacrest". Katie Stevens (Karma) is a former American Idol finalist, and probably said the same things backstage.
Also Karma and Amy's song is "Straight Up" by Paula Abdul, while Paula wasn't on Katie's season, it was memorably performed during the season by fellow contestant Andrew Garcia.
She also speaks Portuguese as does Katie Stevens, who has Portuguese ancestry on her mother's side.
"I'm going to expose Liam for what he really is!" "What, a werewolf?"
When Penelope gives Lauren "exciting news", she retorts "You're finally getting your hair straightened?" Which is what happens to Senta Moses' character Lizzi in Greek.
"Felix is my new...GBF!" (Which is, of course, the name of a film that Faking It writer George Northy wrote and Michael Willett starred in.)
Shane makes a Pretty Little Liars reference, a show which his best friend, sister and principal all appeared on.
In the Halloween episode, Penelope shames Karma for cultural appropriation for wearing a Cleopatra costume when she isn't Egyptian...something she'd have to shame her Italian/Lebanese-American actress Senta Moses for, as she's played Cleopatra for a skit in Beakman's World.
Shane lampshades it in episode 2: "Most of my college boy toys think I'm in college."
And in Season 3, a 23-year-old Katie Stevens plays a 12-year-old Karma for a hilariously bad throwback video. Braces, a bad perm, and probably bound breasts did not quite work.
Disabled Character, Disabled Actor: Wendy, the wheelchair-bound campaign manager introduced in "Busted", is played by Ali Stroker of The Glee Project, who was paralyzed in a car accident when she was 2.
Easter Egg / Freeze-Frame Bonus: In the final episode of season 2B, if you read the names of the school board, aside from the member they're targeting, all the other board members have the names of the writers on the show. At the end, one of the students in Shane's and Karma's lifeguard class is named Aviles, as in assistant producer Gef Aviles. Also in the episode when all the students put on their identity labels, Lauren includes "Libertarian" before mentioning she is one later.
Fake American: Gregg Sulkin is British. Rita Volk was born in Uzbekistan, but emigrated at age 6.
As of the first season finale, Lamy for Liam and Amy (said by both detractors and the rare fan of the pair.)
In season 2, we get Reamy (Reagan and Amy), Shuke (Shane and Duke), and Thauren (Theo and Lauren).
Production Posse: Carter Covington brought over quite a few actors from Greek with him, starting with Senta Moses as Penelope and continuing with Derek Mio as Zen, Aynsley Bubbico as an art critic, and Dilshad Vadsaria as Duke's publicist.