He was Jake Long's imaginary mental image of his potential future son seen in two cases of mental imaginary scenes where Jake imagined what he himself might be like in the future as a father. At first, Jake imagined himself as a grown-up, similar in appearance and attitude to his own father, calling out to "Jake-a-roony Junior" in an embarrassingly geeky fashion.
"Junior" looked a lot like Jake with a thinner face and wilder hair with only three green stripes to the sides and top of his head.
While the first imagination caused Jake "Senior" to shudder in apprehension, after a better appreciation for and spending a day with Jonathan, his next imagination was much more heart-warming.
- "Jake Long Junior" is a product of Jake's imagination, and is therefore not real and does not exist beyond and outside the scope of those two imaginings. Although as Jake's imaginary son, he would still be a dragon; being the figment of an imagination, the question of whether or not any "dragon powers" skipped him was not covered in the imaginary setting, nor important to it. Do not add information about him beyond what was presented in Jake's two imaginary visions.
- "Bite Father, Bite Son" (flash-forward)