Anyone else think that these kids act a bit maturely for their age? I mean, most parents probably wouldn't let their 8-year-old kids bike around a large city on their own. (See "Free Range Children" on TVTropes)

The tough customers act more like teens (TBH, if I ever saw 9 year olds dress like that and act tough as the TCs do, I would think that they were just trying too hard to be "mature")

As for D.W., she has an impressive vocabulary and uses phrases I would never have used when I was 4/5 ("the birds and the trees", as she puts it in "Kiss and Tell", or "Now I know what true power feels like!" in "D.W.'s library card")

It does happen to some. You just never know. Plus it's a cartoon and I don't expect cartoons to be correct all the time.