The character subsequently appears in Daredevil #39-41 (April-June 1968), Daredevil Annual #2 (1971), Marvel Team-Up #25 (September 1974), X-Men #94-95 (August-October 1975), and Iron Man #115-116 (October-November 1978), in which he dies. The character appears posthumously in Iron Man #139 (October 1980) and Classic X-Men #3 (November 1986).
Ape-Man appeared as part of the "Ani-Men" entry in the Official Handbook of the Marvel Universe Deluxe Edition #16, and in the Official Handbook of the Marvel Universe Master Edition #24.
Along with Bird-Man, Cat-Man, and Frog-Man, Keefer was recruited for his great strength by a man named the Organizer to form the Ani-Men. The Organizer was secretly Abner Jonas, a candidate for mayor of New York City, who sent the Ani-Men on missions to undermine the current administration. Daredevil defeated them and the Ani-Men and Organizer all went to prison. Later, Ape-Man, Bird-Man, and Cat-Man formed a team called the "Unholy Three" with the Exterminator, and fought Daredevil again. The Unholy Three, as a team of independent thieves, fought Daredevil and Spider-Man and were defeated.
Ape-Man, Bird-Man, and Cat-Man later rejoined the Ani-Men, and the Ani-Men went to work for Count Nefaria. Nefaria's scientists submitted the unwitting Ani-Men to processes that gave them superhuman powers and animal-like forms. The Ani-Men invaded the Cheyenne Mountain missile base for Count Nefaria, and fought the X-Men.
The Ani-Men lost their superhuman powers and reverted back to normal. Nefaria sent the four original Ani-Men to kill Tony Stark, however the Spymaster detonated a bomb with which he had intended to kill Stark, and the resulting explosion killed the Ani-Men instead.
While employed by the Exterminator, Keefer wielded a "time-displacement ray" ("T-ray") gun that fired a ray which projected its victim into a limbo-like inter-dimensional void. The gun could thus "displace" a victim for a limited period of time, such as 30 minutes. A ray blast of sufficient intensity could exile a victim to the inter-dimensional void permanently.
Keefer was later subjected to an unknown mutagenic process administered by Count Nefaria's scientists which temporarily gave him a build resembling that of an ape, and gave him superhuman strength and enhanced his durability, agility, and reflexes.
Ape-Man appeared as part of the "Ani-Men" entry in the Official Handbook of the Marvel Universe Deluxe Edition #16, and in the Official Handbook of the Marvel Universe Master Edition #24.