Loose Threads:

Does Jane ever get her sketch book back? Why was she so willing to hand it over in the first place?

Why is Brittany's house decorated with so many dead or fake animals?

What happens to the gate crashers?

When Quinn is about to go to bathroom, clocks are set to different times.  One to about 9:50 and another at 8:30.

Does Daria ever get those snappy orthopedic shoes she's been saving up for?

What does Daria do with that sock they steal from Brittany's party?
(She does tell Upchuck to stuff a sock in it when he's driving them home, but does he take her up on the offer?)

Notables:

The houses between where the Morgedorffers live and the school have really big yards and are fairly big themselves. This is a fairly well-off community they live in.

Brittany's birthday is in the month before this episode. A callender in "Esteemsters" set that episode in May, so Brittany was probably born in April or May.

Joey, Jeffy and Jamie are on the football team.

The cafeteria line in Daria's school starts in the desserts section, which is a rather odd design.

First sighting of Trent, Mack, and Joey, Jeffy, and Jamie.

When Brittany complains about the wet lunch trays, and Daria replies "What does not kill us, makes us stronger," she is quoting Freidrich Neitzche. It is a favorite of G. Gordon Liddy, and it appears at the beginning of the movie "Conan the Barbarian."

Trent is a Nirvana fan. However, Nirvana music is, on the whole, rather simple to play (a guitarist friend of mine says it's great for warm-up). If he's having trouble with it, he can't be very good.

Stacy wears her backpack to the party. Fashion accessory, perhaps, but unusual for her crowd if so.

Brittany manages to pick Daria for her art tutor and Jane for her math tutor... not only is she bad at schoolwork, she isn't exactly good at picking people either.

When Daria and Jane are approached by Upchuck, and Daria gives her name as "Esmerelda" , she is saying: "Me Esmerelda, you Hunchback."

Charles knows something about architecture.

The door to the bathroom in Brittany's house is really wide. Maybe so they can fit the Jacuzzi in later.

Upchuck's licence plate number is HS2 19, and his car looks like a Volvo.

Mistakes:

When Brittany is trying to master persepctive, Ms. DeFoe gives her a new pencil and a sheet of paper. Ms. DeFoe says "take a fresh piece of paper" as she does so, but the paper appears to have writing on it.

There are two instances in this episode where the size of the window panes change in close-up scenes. The first is when Daria and Brittany are in line in the cafeteria and the second is when Kevin and Brittany are getting ready for the party.

The mirrors in Quinn's room don't seem to pick up anything besides Quinn. Things behind her aren't visible in the mirrors.

When Quinn spots Daria and rushes off to the bathroom, two different clocks are visible with very different times showing. One points to 10:45, the other 8:30.

Double Meanings:

Brittany and Daria are standing at the lunch counter together
Brittany: Ewww! I hate it when the pudding has skin.
Daria: I know what you mean. And that scares me.

Now, watching the videos, it seems as if Daria is implying that Brittany is a pudding with skin... if it wasn't for the "And that scares me" part of her comment, I'd be sure of it. Personally, I like this meaning better.

The mirror picking up Quinn's reflection and nothying else made me think...could this Mean Something? Could this "reflect" (huh huh) Quinn's attitude towards her life (she thinks about herself but no one else around her?)
Note: This is also a standard animation practice, but that doesn't mean it can't mean this too.

Kevin and Brittany are at Brittany's house, setting up for the party.
Brittany: I love being the hostess, it's so easy to home at the end of the night.
Kevin: You're a great hostess, cupcake.

Kevin calls Brittany a great hostess and cupcake, but says them right after each other, thus saying Hostess Cupcake. This is the second time in the same episode that Brittany is, somewhat obliquely, reffered to as sweet, sugary, but empty of any real value.

When Trent drops Jane and Daria off at Brittany's party, they ask if he'd like to crash. He says that he's too mature for a high school party (basically saying he'd never go to a high school party). Then he says to Jane and Daria "Don't do anything I wouldn't do." I like the irony here.