Character type: Snide, villainous henchmen
Examples: The weasels in The Wind in the Willows, the weasels in Who Framed Roger Rabbit
If your name openly suggests a certain character trait, it makes it difficult for casting directors to think of you as anything else. For instance, it would be tough to cast an actor named Barry Leading-Man as anything other than a protagonist. Or a bloke called John Wacky-Sidekick as anything but... You get the picture. Anyway, since 'weasley' has come to mean snide, cowardly and generally unpleasant, these types of roles are all the poor weasel is ever offered. To add insult to injury, they're never considered for the main bad guy - only his nasty, spiteful henchmen.