The Sun represents vitality and warmth, childish fun, success, and general positivity. Reversed, it is the inner child, being overly optimistic, or feeling down. So... Pinkie Pie.

The four balloons represent the four elements or four suits of the minor arcana. The sunflowers represent light and vitality. The birthday blower represents the fun and joy of being connected and at peace with yourself, having nothing to hide and only the happiness and contentment of this moment when you are making a goofy sound and giggling about it.