Season 1

After an unsuccessful paintball match, the four physicists make their way to Sheldon and Leonard's apartment. Once there, they encounter their neighbor Penny, who is throwing a party and invites the four nerds. At first, the four wanted to decline the invitation. But when Penny explains to them that it is a Halloween party, they change their minds and decide to take part in this ceremonial activity. Full of anticipation, each of the four goes to get an appropriate costume. When they later meet again, they unfortunately discover that they have all decided on Flash the Red Lightning . Since they cannot all go as the Flash and nobody wants to give in either, they agree that nobody will go as the Flash instead. After another organization round, the costumes have been decided upon. Leonard is going as Frodo, Raj as Thor, Sheldon as the Doppler Effect, and Howard as Robin Hood. Although everyone sees him differently as Peter Pan. Punctually, at the agreed upon time, the four show up at Penny's apartment and at once discover that they are not only there too early, but also that there will be no jury for the best costume.

At a later time, when the party is already in full swing, none of the four can really bring themselves to have a conversation with the others present. Except for Howard, who intends to be different, and speaks to a woman for the others. However, without success. In the meantime, Leonard and Sheldon have also overcome themselves and force themselves to converse with the other guests. After a conversation or two, it is incomprehensible to Sheldon that everyone will take him for a Zebra and not for the Doppler Effect.

Out of the blue sky appears Penny's ex-boyfriend, Kurt. Leonard is not particularly delighted about this and decides to duel intellectually with Kurt. When Leonard gets his courage together and shows Kurt that he is mentally superior to him, Kurt becomes violent. Luckily, Penny becomes aware of the whole drama and gets between them. After Penny has solved the crisis, Kurt walks away, and Leonard says goodbye and goes back to his apartment. A little later, there is a knock at the door. It is Penny. She would like to apologize to Leonard for the behavior of her ex-boyfriend and to make sure that Leonard is okay. When Penny tells of the whole history between her and Kurt, she breaks into tears. Out of sadness or, more likely, because of the high level of alcohol in her blood, she kisses Leonard who is a little overwhelmed with the situation. After he realizes what is going on, he pushes Penny back because he doesn't want to take advantage of her drunkenness. In the doorway, she says goodbye with another kiss and goes back to the party. As coincidence would have it, Kurt was in the stairwell and saw the kiss. Leonard is once again on top of it and brags about how much Penny would find pleasure in him, and quickly locks the door so that Kurt cannot come after him.

The next morning Sheldon is rudely awakened. Howard knocks on the door, because he has not seen Raj since the party and now he cannot find him. As it turns out, Raj spent a night with a girl who really thinks that he is a good listener.