A "May/December romance" is a love affair where there is a significant age difference between the two partners. The two galleries, the Zelman and Offerman, are named for Debra and Megan's husbands (Daniel Zelman and Nick Offerman).
Grace: You just made the biggest mistake of your life, my friend.
Karen: Big mistake.
Grace: I am not someone that you want to trifle with.
Karen: You don't want to trifle with her.
Grace: You are gonna rue the day that you ever messed with Grace Adler.
Karen: Grace Adler is a mess.
Grace: I know a lot of noodle lovers. And when I tell them what happened at Happy Noodle, they're gonna snub you hard and walk the extra ten feet to Lucky Noodle. Good-bye. (Grace leaves the restaurant)
Karen: You hear that? She's bi!
Jack: What are we gonna do tomorrow night?
Will: Well, I was gonna go to this art opening.
Jack: Ooh, that sounds great. I'd love to join you.
Will: It's not a person named "Art," you understand?
Jack: (Sighs and rolls eyes.) Yes, I know.
While filming the part when Grace drops the noodles and then walks out, Debra almost fell on the first take. So on the second take they had the noodles cleaned before having her walk out.
At the beginning, Grace says the restaurant's name is "Happy Noodles", while the menu says "Happy Noodle". Yes, the difference between singular and plural. Still--it's a goof. Later, Grace said "Happy Noodles" again, while sitting on the couch telling her friends not to go there.