Poorly-Aged Franchise

''But not like some disease that'd cause your skin to go yellow and give you an overbite. Not that kind of Simpsons disease.''

The Simpsons' Disease is a somewhat uncommon condition that causes franchises to lose sight of what made them so likable when they were new. It's called that for... obvious reasons. This would normally be fatal as it causes the franchise to either be cancelled or become a Zombie Franchise if it's continued. Simpsons' Disease can infect franchises much easier if they're rebooted or given unwanted sequels.