Has an AFL game ever ended 77-31?
Exactly once. On August 21, 1909, Fitzroy beat St Kilda 77-31, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 77-31 in league history.
That makes 77-31 the 3884th most common final score out of 6,649 that have ever occurred in AFL. One point away, 78-31 has happened 2 times and 77-32 has happened 2 times.