ADVENTURES OF SUPERMAN #500

1st cameo appearance of John Henry, later becomes Steel
1st cameo appearance of Superboy, Conner Kent
1st cameo appearance of Cyborg Superman, formerly Hank Henshaw
1st cameo appearance of the Eradicator
*each of these characters claiming to be Superman were introduced in full in separate issues that all went on-sale on the same day
1st appearance of Angora Lapin, later becomes White Rabbit