Archetype theory
Deep in everyone’s mind there is a stock image of a creature that is glad to see you. When life gets heavy, sensitive sleepers reach for it, and it comes out as a ginger cat with dinner-plate eyes. “Hi” is the entire message: you are not alone.
Religious theory
THIS HI is a higher power that has decided to keep things simple. If it greets you, greet it back. Some believe that whoever ignores the hi will be said hi to again, and again, until they answer.
Dream surfer theory
Out there is one real cat that can wander from dream to dream the way cats wander from room to room, uninvited and unbothered. Some suspect it is part of a plan to make the whole world say hi at once. Of all the theories, this one has the least science behind it and the most fans.
Dream imitation theory
Nobody dreamed of the cat at first. Then one person did, told a friend, and the friend dreamed of it too. Every repost makes more people fall asleep thinking about those eyes, and the hi spreads like a yawn.
Daytime recognition theory
Nobody remembers faces from dreams very well. You saw the cat somewhere on your feed, and the next time a vague animal turned up in a dream, your brain filled in the blank with the face it already had on file. The “Hi” is your own.