Deandra "Sweet Dee" Reynolds is Dennis' twin sister and the main bartender at Paddy's.  Sweet Dee was definitely considered a loser in high school thanks in part to her back brace she had to wear back then.  Sweet Dee failed out of U Penn, where she studied psychology.  Now, she's mostly a failed actress and stuck as a bartender with her brother and his friends.

Deandra "Sweet Dee" Reynolds Quotes

Charlie: what is your spaghetti policy?
Dee: Are you hearing this? He doesn't belong in a place like this.

Dee: You've been really stressed so I thought I'd take you to a spa day. Just the two of us.
Charlie: A what day?
Dee: Spa day
Charlie: What is this word, spa? I feel like you're starting to a say a word and you're not finishing it. Spaghetti? Are you taking me to a spaghetti day?

It's Always Sunny Quotes

Mac: Bro, when you tack on mass, you sacrifice flexibility. That's just a straight up fact
Charlie: That's insane. Touch your toes.
Mac: What am I a gymnast?

No I don't eat dragon, cause, uh, it's not a meal for peasants, it's a meal for kings, and I'm sort of a common man. But they don't eat us, it's a common misconception. They actually eat gold and treasure -- that's why they're always sitting on a pile of it.

Charlie