Exposing oneself or masturbating on a plane while sitting next to a national newspaper journalist and in front of flight personnel. Whilst drunk / on "painkillers" for a "neck injury".
And having NO recollection of the event what so ever.

Strictly not illegal, but is frowned upon.

The horrible moment when you realise that you have accidentally done something very slightly wrong which has very bad (usually embarassing) implications for you. This is typically the moment of realisation that you just sent a dirty text message to a close member of family, typically your mother, rather than the intended recipient.