As a part of their monthiversary, Andrew and Zelda plan a joint Halloween party to celebrate. Once they send the invitations, Zelda feels bad knowing that she, and Andrew, have strong Halloween traditions with Stephie and Stu. When they discover the party, Stu and Stephie are furious with Andrew and Zelda. 

They make amends and allow Stu and Stephie to co-host the party with them. As the party planning continues, Stu and Stephie begin to take over the plans, creating their own separate themes. Since Stu and Stephie cannot agree on any plans, Andrew and Zelda cancel the party.

At Wallflower, Big Bird wants to invite the most attractive, successful couple to their Halloween party. Unfortunately, the couple have a violent, domestic dispute and cannot make it to the party. When Big Bird and Howard are unable to find another couple, she sees the happy couple, Andrew and Zelda, and forces them to be the signature couple for the Wallflower party.

When they go to the party, Andrew and Zelda are not happy being the "it" couple for Wallflower. Stephie and Stu show up in their traditional costumes, Laverne and a Ghostbuster, to make Andrew and Zelda jealous. Big Bird gets sick of the bickering so she sends the four of them to a separate room. 

Stu and Stephie finally air their grievances about Andrew and Zelda's relationship. They don't want to be replaced as best friends as Andrew and Zelda become closer. They all apologize and spend the rest of Halloween in their traditional costumes, as best friends.