Remember in the history when I said that the Obliviate charm still follows him round? Good, cause Jack doesn't. The effects of whatever spell was cast upon him has messed with his head to this very day, as Jack's convinced that it must have left holes in his short-term memory. Literal holes. You see, Jack has a habit of forgetting things. Mostly minor, insignificant things - when dinner time is, where he left his belongings, what day or month it is. Other times, it's slightly bigger; his date of birth, other people's names... he's even forgotten his own name a couple times. Luckily one of his friends is often there to remind him, and if not, he'll just make one up for the time being. He does that for a lot of things; if he can't remember something, he'll just make something up in place of it. He's certainly spilled some tales over the years he can recall.
But sometimes, it goes deeper than just short-term. The lines between right and wrong are somewhat blurred for Jack, simply because... well, he can't remember what they are. He won't think twice about stealing or lying or even manipulating, simply because he doesn't understand what he's done wrong half the time. The realisation that what he just did maybe was a bit of a dick move will often hit half way through his punishment, but sometimes it doesn't return whatsoever, and he spends the day confused as to why he's being shouted at.
Outside all the memory problems (and when he's aware that thievery is indeed against the law), Jack's a sweet kid. He's a little ray of sunshine, and no, it isn't his hair - the guy's just a naturally happy person. He's incredibly clumsy, often says dorky comments and comes out with silly jokes and puns, and his shoelaces will always be untied (how do you tie them again?). Sometimes he can be very gullible, other times he'll struggle to take anything seriously, but he knows how to have a laugh and that's important for a kid. He's a huge chatterbox - honestly, the boy can keep a conversation going for days - and very rarely will you find him in a bad mood. He's also very creative - don't let him loose with a paintbrush, your walls will be orange, but give him clay and a sculpting knife and he'll be making all sorts of figurines.
He's also a huge romantic. Even though he's young, he loves romance films, adores love songs, and thinks Valentines cards are a work of art. Being the perfect gentleman is his goal. He's more than subject to having starry-eyed crushes on every cute girl he sees, and just you wait until you hear about how he chose his name.