June 1st is Oscar the Grouch's birthday - the day when he is at his absolute grouchiest. In episode 3866 of Sesame Street, after Oscar reads a birthday card from his mother, and after hearing Oscar tell the viewers that it was his birthday, Telly Monster tried to give Oscar a grouchy birthday party, something that Oscar thought he couldn't do. In the end, however, Oscar was proved wrong. He received many grouchy rotten gifts.
After receiving a Spanish birthday poem from Maria which translates to: "Happy greeting to you, irritating Grouch. Have a rotten day from here on out!", a promise from Big Bird saying that he won't talk to Oscar the whole day, an empty box from Gina, which he thought was from Grundgetta, and a triple layer birthday cake made with chicken and mint, with sardine frosting from Alan, which his mother used to make, and after hearing everyone (including Bob and The Grouchketeers) on the steps of 123 Sesame Street sing "Grouchy Birthday to You!", Oscar admits that he was wrong--everyone knew how to celebrate a Grouch birthday - until Telly gives him hugs and kisses as his present.
Another party favor was, Luis, Gabi, and Rosita let Oscar play a game: he tries to crack open a trash can-shaped piñata. He succeeds, and is buried by a pile of small junk pieces, torn newspaper, and fish bones. At the end of the day Oscar finishes the cake and announces the sponsors. He notes the best thing about having a birthday: you have to wait a whole year until the next one!