North West and Penelope Disick want friends to wear casual mermaid attire for their birthdays.

North West had her 3 years birthday party on Saturday in fancy Bel Air. Her parents threw her a big birthday bash continuing the the Disney-themed celebration "The Little Mermaid". According to TMZ, Penelope, her cousin, who would be celebrating hers early next month was around too. The birthday bash was thrown for both of them. The birthday celebration continues in Disneyland on Thursday.