1x18 - Shugo Chara!

Tadase invites the other Guardians to an aquarium, however, only Amu is able to go. Amu begins to panic as the trip turns into a date with Tadase but she eventually calms down. As Tadase is about to tell Amu something important, they are interrupted by a little girl who quickly become attached to Tadase. As Amu and Tadase wonder what to do with the little girl, they spot an X Egg floating above the crowd. The egg takes off and Amu chases after it, but the little girl keeps Tadase from following. As Amu is about to catch the egg, she runs into Yoru who is carrying the Dumpty Key. Yoru tells Amu about the Dumpty Key, but the X Egg swoops in and steals the key. Ikuto arrives and chases after the egg with Amu, as Amulet Heart, following. Working together, they finally purify the egg.