Years ago, when I applied for the role of (this) Lyle in a Legion RP, this is some of what I wrote:
"A relatively well-adjusted boy genius, enjoying the practical fruits of his amazing brain. Where Brainy is the theoretical researcher, Lyle is an inventor - he likes to try his ideas out and see what happens.
Lyle likes surprising people, something his power is well-suited to. He's not exactly a snoop (like he's "not exactly" afraid of heights), but he will sometimes use his powers just to get an amusing reaction from others when he appears out of nowhere or springs a new invention on them.
A good model would be Tom Swift, another young adventurer/scientist; in fact, Lyle may have read those stories when he was younger."
One other note was that he really does respect B5 and would like to collaborate more with him, but Brainy does not work or play well with others.