The episode of SpongeBob SquarePants that features Leif Erikson Day is "Bubble Buddy". In the episode, SpongeBob wakes up wearing a Viking costume and proclaims it to be Leif Erikson Day. He then goes outside to celebrate, but his friends are too busy to join him. SpongeBob creates a new friend out of bubbles, named Bubble Buddy, to celebrate with him.