Buffy the Vampire Slayer

Xander: Festive piñata? Delicious candy? Piñatas are hollow cardboard or papier-mache figures usually filled with candy or toys. Piñatas are most often used at birthday parties where they are suspended by a rope, people are then blindfolded and try to break open the Piñata with a stick so that the contents spill out.

Xander: (about the planets) Look at how teeny Mercury is compared to, like, Saturn. Whereas in contrast, the cars of the same name...
Mercury and Saturn are, obviously, planets. They're also American car companies. Saturn is a newer company which currently sells 3 series of vehicles — the L-Series (mid-size sedans/station wagons), the SC-Series (sporty coupes), and their most popular S-Series (compact sedans). Mercury is a subsidiary of Ford Motor Company, which manufactures mid-to-full-size sedans and sport utility vehicles.

Willow: (looking at the stars) That's Canis Minor, and Cassiopeia.
Canis Minor is "the lesser dog," one of Orion's hunting dogs. Cassiopeia is Andromeda's mother from the legend of Perseus. Both of these stars are most visible in North America between November and March.

Dawn: There's a girl at school told me that gelatin is made from ground-up cow's feet, and that if you eat Jell-O, there's some cow out there limping with no feet.
Dawn isn't as far off as Buffy would have you think. Gelatin is a protein which is obtained from collagen, typically from cows' bones and skin. The bones and skin are immersed in acid, and the eventual solution is processed to make gelatin.
Jell-O is a specific brand of gelatin dessert. It's common to refer to all gelatins as Jell-O, kind of like Kleenex.