So Merv and his follow gryphons were an engineered species. When they were made, their language Aves had math baked into it. This was useful for a bunch of wormhole maintaining bird cats. It also meant that when they talk about things, they use radians. So they never use the word behind in their own language. It's just π ... π radians is 180 degrees. Fast forward several millennia. Most of the gryphons and other myths have nackered off to Ring so the humans can develop in peace on Earth. However there is still some contact and even some humans that wound up on Ring for various reasons. English is a second language for them, so if some gryphon slips up and yells π out loud, it meant 'behind you'.

A new tradition has appeared in the last 50 years or so, which is pretty recent by many myth's measuring of things: Pi day, only on Ring. On March 14th, gryphons and sphinx surprise their human friends with a shout of π from behind or vice versa. In their talons, paws, or hands is the screwed up invention of a fae baker: The symmetry breaking pie. A point where Schrodinger's Cat meets baking. This pie is either a fruit pie or a whipped cream pie. Until the recipient sees it, no one knows.

Fruit pies are eaten, whipped cream pies are... well. It is their new version of April Fools Day after all.