Get all the Sunday School classes or mid-week classes involved with this one. Each kid in each class gets an offering container with a photo of their teacher on it. The kids collect offerings over a designated period of time, such as a month. The class that brings in the most money gets to have their teacher kiss a pig.
Another options is to do "Boys versus Girls," and whichever group brings the lesser amount of offering, their leader has to kiss the pig!
Or if you'd prefer to get the whole congregation involved, then have offering containers for each of your pastors. Whichever container ends up with the most money, that pastor gets to kiss the pig!