Leif Erikson Day is an annual observance that occurs on October 9. SpongeBob SquarePants celebrates Leif Erikson Day in the episode "Bubble Buddy". In the episode, SpongeBob calls out "Hey everybody, its Leif Erikson Day! Hinga dinga durgen!". This episode has become a popular reference for the holiday among SpongeBob fans. Therefore, Leif Erikson Day is celebrated on October 9 in the SpongeBob SquarePants universe.