You're right about the Unca
Donald number, Weslyn, but I think you mean license "PLAQUE", altho here you'd say license "plate" or "tag".
Don't know what "PLAGUE" is in Danish, but in
German it's "die Pest". (That well describes the people you've gotta see to get em, but not the thing itself).
Two other well-known license plate numbers in popular culture are "28 IF" and "THX 138". Do you know the origin of either of those?