Kid!Arthur/Merlin: First Day of School.
Finally got some inspiration!
Hunith: Are you boys ready for your first day of school? Show me how excited you are! Give me your biggest smiles, okay?
Merlin: Cheeeeeese!
Hunith: Arthur, where's your smile?
Arthur: ... I don't wanna go to school. *pout* I wanna stay home and play with Merlin! *wiggles elbows petulantly*