Happy Birthday to You
"Happy Birthday to You" is a song commonly sung for someone's birthday.
Background
In "Death", it was first sung at the beginning of the episode. Stan, Shelly, Sharon, and Randy had came along to the dining table in their residence to celebrate Marvin's 102th birthday. Marvin tries to blow the candles off his cake but fails, he then claims that his only birthday wish is to be dead.
In the post-credits of "Mr. Hankey, the Christmas Poo", Jesus sings to himself alone in the Jesus and Pals Set of South Park Public Access. He blows off his candles off his cake, leaving the room all dark.
In "Casa Bonita", Cartman caught everyone off-guard when he tried to decline that Kyle should decide what to do in Casa Bonita since it's his birthday. He tried to get that off everyone's minds during the car ride and sang "Happy Birthday" with the others.
Stan sings a portion of the song in "Stan's Song" in "Elementary School Musical" when the kids in the hallway expected him to sing.
It was also sung at the beginning of "You're Getting Old" in Stan's birthday party at Whistlin' Willy's.
In "A Boy And A Priest", it was Clyde's birthday at the Kidzone Roller Rink. The children at his party sang along while Clyde blows the birthday candles. Father Maxi then tells the children to pray for Christ, which everyone groans as a response.
In a Zoom session in South Park: Post Covid: The Return of Covid, there was a virtual birthday party for Stan.
Lyrics
Normal Version
Happy birthday to you,
Happy Birthday to you,
Happy Birthday, dear (name)
Happy Birthday to you!
Solo Version ("Mr. Hankey, the Christmas Poo")
Happy Birthday to me,
Happy Birthday to me...