Georgian's grammar swaps who counts as the 'subject' depending on tense

In most Georgian tenses, subjects work like English ones: 'I' stays 'I' whether it sleeps or hits someone. But switch to the aorist (simple past), and the subject of 'I hit him' takes a special ergative case, while 'him' and the subject of 'I slept' share a different one. Linguists call this split ergativity.

— Wikipedia contributors, Georgian grammar — Wikipedia, 'Case system' / split ergativity section