Flim-Flam is a clever child who briefly joined the Mystery Inc., and assisted them will prove it is not a real ghost.
Flim-Flam wears a yellow tracksuit (which contains a hyperbolic amount of stash -- probably ill-gotten). He has an unkempt mop of black hair and wears sneakers. He is about a foot taller than Scrappy-Doo.
Flim-Flam is, as his name implies, a born scamster and opportunist. Although tremendously ambitious, he doesn't seem to be above bilking and bamboozling people for his own profit. While he is more or less on the level with his friends, he does tend to exaggerate his abilities and past deeds.
He is also a know-it-all and cracks quips and jokes more often then the rest of the gang, and seems quite confident in his (rather proficient) ability to smooth talk his way out of a situation (usually prefaced with a smarmy, "Hiya, neighbor! What can I do ya for?"
While on friendly terms with Fred, Velma, Daphne, Scooby-Dum, Yabba, Dusty, Scooby and Shaggy, Flim-Flam has a close brotherly relationship with Scrappy (perhaps due to their common youth and short stature). However, Vincent Van Ghoul seems to have a bit of reservation and doubt dealing with Flim-Flam -- probably due to Vincent being all too aware of Flim-Flam's shady tendencies.