1. It is performed in a seedy location, i.e., a parking lot, a Burger King bathroom, a public bus, or anywhere in New Jersey.
2. It is mutually casual to the extent that both (or all) parties involved can and do openly discuss the event with no shame, regret, embarrassment, or passion; though they may recall it fondly.
3. It nonetheless somehow scandalizes a third party who had nothing to do with the act.
Usage note: drunk calla is a non-count noun, meaning it isn't typically pluralized and takes no article ('a', 'an', or 'the'). Simply put: use the term as you would use the term head.