A vacation whose primary purpose is to fulfill an obligation or obligations, usually ones that are not enjoyable. (E.g. visiting disliked family members, attending memorial services, weddings you'd rather not attend, etc.)
This summer we are going on a vacation to Paris and an oblication to Toronto. My sister is holding Mittens' annual cat memorial service in July. It's pretty far to drive, but we'd never hear the end of it if we weren't there.
An Obligatory Psychotic Jackass refers to somebody who is self-elected as the rude, obnoxious and possible bully of the school. An example of this is Logan Echolls off the fictional television show “Veronica Mars”
VERONICA MARS: And let’s not forget Logan Echolls. Every school has an obligatory psychotic jackass. He’s ours.
YOU: "Oh my god! Look at that guy! He's a total obligatory psychotic jackass!"
ME: "Yeah, he acts like early season one Logan Echolls!"
Ivar wanted to let his friends know that he was drinking and beeing all cool, but lowkey. So he uploaded a picture of a vodka bottle and a package of digestive cookies, and said that the digestive cookies were obligatory, therefore Obligatory Digestive.