I'm not sure what brought it on, exactly. It just seemed like a good idea at the time.
It's an interesting concept, but also a little scary. We know so little about Jonas' background that all sorts of possibilities are opened up. Sure, with the other characters there is definitely room for a writer's creative interpretation of known facts... but with Jonas, those facts are pretty scarce. We know he worked as a kind of government advisor on Kelowna and that he was pretty close to one of the creators of the naquadria program. We know that his planet has basically been in a cold war for the last twenty years (meaning there was some kind of real war during his childhood). His intelligence and ability to learn quickly probably made him a pretty attractive resource. But as far as hard facts, that's about it. Unless I'm missing something.
Character traits are a little more interesting, from my perspective. The boy definitely has issues with proving himself. He likes to try new things -- like food ;) He seems to truly enjoy learning. He has a sense of humor, but maybe not so heavy on the sarcasm as some. He's loyal.
Which is all good to know. The question is, how does is translate into a story?
Now, I only have a page written at the moment, so I can't really say definitively. I do know what I want to do... construct a backstory. Explain how he became entwined in the SG-1 universe, all the way back to when he took the job that placed him in that room on that day. And while I'm hardly a psychologist, I would even more like to explore (aka, make up) things about Jonas' family and culture to give rise to the above personality traits.
And I want to give him a girlfriend. The boy needs a girlfriend.