: Wearing a skin-tight bodysuit with vertical black-and-white lines, Sheldon spends the evening making a "Neeeeooooowwwww" sound to represent a shifting frequency wave, a joke that remains entirely over the heads of the other partygoers.
: Complete with hairy feet, Leonard chooses a costume that he believes makes him look adventurous, though he is frequently mistaken for an Elf. 6. The Middle-Earth Paradigm
The episode centers on a Halloween party hosted by Penny, which marks the first time Leonard and his friends attempt to integrate into her social circle. The Costume Crisis 6. The Middle-Earth Paradigm