Why did jack flack jump up and down and twist all around before taking his medicine?

Jack Flack jumped up and down and twisted all around as a playful way to express his excitement or perhaps to distract himself from the unpleasantness of taking medicine. This whimsical behavior could also serve to lighten the mood, making the experience more enjoyable. Ultimately, it reflects a child's way of coping with a situation they may find disagreeable.