Buffy the Vampire Slayer

Xander: Only in an erotic, Penthousey way, not in a sponge-bathy geriatric sort of... Penthouse magazine is a sister magazine to the adult Playboy by the same company, which depicts letters from readers of an erotic nature.

Xander: Dependable? What is he, State Farm? State Farm is an insurance agency started in 1922. State Farm markets reliability as its main selling point, its slogan is, "Like a good neighbor, State Farm is there." It orignially specialized in auto insurance for farmers, but now offers other popular types of insurance, such as homeowners, life insurance, financial services and banking.

Major Ellis: We have a Code One in Belize.
Belize is a country in Central America located on the Caribbean Sea. It is a former British Colony that became independent in 1981.

Anya: Strawberry schnapps tastes just like real ice cream. Schnapps is a generic name for a flavorful, usually clear alcoholic beverage made from fermented grain and flavored with various herbs or fruits. Schnapps can come in a variety of flavors including strawberry, peppermint, orange, butterscotch, and many others.

Anya: Well, we could play that game again - Life? That was fun. The Game of Life is a classic board game now owned by Hasbro. It consists of between 2 and 10 players each getting a plastic car in which they can collect their "family" throughout the game, as they progress they collect cards with life events on them. The player with the most money at the end of the game wins.

Xander: So, what do you wanna do now, Dawnster? Keeping in mind that I won't chase you because I'm old and I'm stuffed full of moo goo gai starch. This is a reference to Moo Goo Gai Pan, a Cantonese dish of chicken, mushrooms, vegetables, and spices sautéed together.

Title: Into the Woods
"Into the Woods" is a musical by Stephen Sondheim that brings together several popular fairy tale characters and plots.

Xander: (about Buffy) Yeah, when we went to deal with that vampire nest, she got all Rambo and torched the place.
Starring Sylvester Stallone as the eponymous Rambo, a mentally unstable Vietnam war veteran, this was a famously violent action movie trilogy consisting of 1982's First Blood, Rambo: First Blood Part II in 1985, and Rambo III in 1988.

Visual: Winter Solstice, Hanukkah, Christmas, Kwanzaa, and Gurnenthar's Ascendance
Many religions have a celebration around the time of the Winter Solstice (the shortest day of the year in the Northern Hemisphere, which falls between 20-23 of December). The few mentioned on Giles' banner in the Magic Box were:
Christmas: A Christian festival celebrating the birth of Jesus Christ, on December 25th.
Hanukkah: An 8-day Jewish celebration commemorating the victory of the Maccabees over Antiochus, the king of Syria, in the 2nd century BC. It begins on the 25th day of Kislev. This fell on December 22nd in 2000.
Kwanzaa: Created in 1966 by African-Americans to promote their needs, in response to Christmas, which they felt did not represent them. It is celebrated between December 26th and January 1st.
Gurnenthar's Ascendance is apparently made up.

Buffy: Are you planning to seduce me, Mr. Finn?
Likely allusion to The Graduate, a 1967 movie starring Anne Bancroft as an older woman and Dustin Hoffman as a college-aged guy. The most famous line from the movie is "Are you trying to seduce me, Mrs. Robinson?"