Has an AFL game ever ended 91-8?
Exactly once. On August 12, 1961, St Kilda beat Richmond 91-8, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 91-8 in league history.
That makes 91-8 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 92-8 has happened never and 91-9 has happened never.