Has an AFL game ever ended 37-20?
Exactly once. On June 24, 1899, Melbourne beat St Kilda 37-20, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 37-20 in league history.
That makes 37-20 the 3884th most common final score out of 6,649 that have ever occurred in AFL. One point away, 38-20 has happened never and 37-21 has happened 2 times.