Do you think that when McGonagall really got tired of her colleagues’ shit she just turned into a cat and started doing random cat things? Like:
Dumbledore: Minerva, please, I really have to send those letters
McGonagall: *gets more comfy over Dumbledore’s desk*
Dumbledore: Minerva
McGonagall: *starts chewing on a nearby quill*
—
Umbridge: why are the cushions in my office so ruined? Who is responsible for this?
Every other teacher:*glances to McGonagall*
McGonagall:*cleans her nails*
—
Snape: Minerva get out of that jar now I need it
Snape: you are far too old for such antics
Snape: I’ll stop taking points from Longbottom for a week, is that enough?
McGonagall:*flicks her ear*
Snape:…how did you even get inside there
McGonagall:*meows and burrows deeper in the jar*And thus we have found my absolute favourite Harry Potter Headcannon.