I wonder if the Dwarves scottish accent thing may have originated as a sort of "Highlands" parallel. Dwarves being mountain dwellers, scotland being mountainous/hilly and the like. Both having a reputation as hardcore drinkers. Etc.

__________________
[Dr. Horrible]___________________________[Penny]
Listen close to everybody's heart________And you believe there's good in everybody's heart
And hear that breaking sound_____________Keep it safe and sound
Hopes and dreams are shattering apart____With hope you can do your part
And crashing to the ground_______________To turn a life around