The Get Big Town ad is a flyer given to the inspector by the fifth entrant on day 28. The entrant giving it is likely either the owner, an employee, or a very enthusiastic customer of the Get Big Town gym. They promise to transform the inspector from a "skinny weakling" into "big" – if he joins the gym.
The Get Big Town is located in East Grestin and is advertised as the "best gym."
The ad and the entrant giving it have no effect on the gameplay beyond exposition. The ad cannot be given to anyone and will not be in the booth on the next day.