[Dr Fred]

Not only the accent, but the behaviour and their appearence.

Dutch are much louder than the Flemish, who are unconspicuous and soft-spoken. Dutch are direct while Flemish are consensual. In some ways their idiosyncracies are diametrical opposites. Physically, the Flemish have less superficially "tall big blond" types you find in the Netherlands, they are more Keltic/Atlantid. An exemple of a typically Un-flemish, typically Dutch appearance is Theo Van Gogh.

The low-profile behaviour of the Flemish could be linked, if you ask me, to what I wrote in an earlier post about Walloons: the Belgian state cultivates a non-culture and a deliberate lack of pride, so they were prevented to be too culturally boastful in order not to disrupt the geopolitical order of things, IMO.