Ok but Of all days, Gary wanted to go with his father that specific day The caterpillar was his gift John's only concern for leaving was to not get to see his son grow up Gary has never been seen talking about his bday What if... John died on Gary's birthday?
I have this headcanon that before John death, on every birthday Gary would save one piece of his cake for his mother, hoping she might come to his special day. She never came