Young Flint was the weeping one. He did not at all weep, but upset himself because of school. Since he was so young, Fran talked about that being a nerd is alright. After he was mocked and teased at school, Flint realized that he didn't have to involve about it, his mom gifted him a professional-grade lab coat to cheer him up, and then told him to make more inventions; so he wrote up a "Best Inventor Ever!" note on a piece of paper and then excitedly ran over to his tree house to finish up his projects. From that moment on, he was determined to invent something great, like "Remote Control Television" and onward. Young Flint had a very simple story and a very short voicing process, he also had very small screen time so he doesn't come out much in the whole movie.
Young Flint promptly comes of age during the beginning of the movie, but from that point, Flint still had the mentality of a five-year-old, but still remembered not to get upset when things don't go right.
Around ten (when his lab was half it's current size that time),he first became Inspired by Chester V as he used to watch his television programs & eat his official food Bars.