You'll write a script that feeds into a bigger campaign... He'll insist you use his revised script because it's funnier. Then he'll refused to read your script because he wants to only do his version.
He'll not sign off on a poster for league of their own because he looks fat compared to Redknapp, Flintoff and the other guy. He insists you have to make him look thinner.
He'll chime in a day before the promotional ad for his show goes to air because he decided he doesn't like the music used (despite being ok with it 3 weeks ago), now you're working all night to edit it from scratch.
Etc etc etc