On the island there is a berry bush and once a year the bush produces ONE berry that is saturated with magical power. This berry is a product of many things lining up perfectly. The sun being bright and warm enough, the way the branch the berry is on is positioned, and what species of bee pollinated the original flower all comes together to make this potent little sphere.
Bubbles didn’t know any of this when she took a flying chomp at the tastiest looking fruit she saw and to her surprise, and the surprise of her two Phomish companions, she was shot through with concentrated magical energy. Bubbles changed different colours, lit up, shot magic out of her eyes, summoned wind gusts and finally flopped on the ground after she had swallowed the berry and had spent all of it’s magic.
Normally the berry would have energized a more skilled magic user, giving them a boost to their already practiced skills. Bubbles, only having her Joynobori form as her magical link, had no such ability and instead gained power she couldn’t control for a very short time. Bubbles was exhausted and took a nap under to bush to recoup her strength. Maybe she wouldn’t try eating berries for a while, just in case.