I feel like Mickey Mouse is really a special case - Disney employs literally thousands of people promoting their IP, and MM's been in constant ongoing and heavy

I feel like Mickey Mouse is really a special case - Disney employs literally thousands of people promoting their IP, and MM's been in constant ongoing and heavy use by them since the start. Mickey Mouse isn't a 'sitting on their laurels' situation - it's an actively worked bit of IP - not something that would be described as 'passive income'.