Somebody needed to drum up business for the repair shop, and since Emmet as usual couldn't be bothered tending to the wellbeing of his own enterprise, the task naturally fell to Sully.

I don't think Emmet would have come up with the idea of a "loyalty card"—and in fact I'm sure Sully almost didn't either. That absolutely strikes me as something that plopped out of his brain while he was in the act of designing the posters.

After having many copies printed at great expense he proceeded to post them all around town, then stuffed what he had left in people's mailboxes, on the windshields of their cars and down their chimneys.

Poster commission by  rockysfplaya
Original Emmet & Sully artwork by  eighteas