A young man in the Diocese of Madison recently posted on his blog (HERE) a photo of the jolly sign at the chancery marking the parking place of the local bishop, His Excellency Most Reverend Robert C. Morlino.
Can. 1340 §1 A penance, which is imposed in the external forum, is the performance of some work of religion or piety or charity.
§2 A public penance is never to be imposed for an occult transgression.
§3 According to his prudent judgement, the Ordinary may add penances to the penal remedy of warning or correction.