X-Men: Evolution Season 4 Episode 8

The outfit Boom Boom wears is the one she used in "Walk on the Wildside."

In the comics, the Four Horsemen more or less chose to serve Apocalypse in exchange for health, strength, or their old powers back. In Evolution, Apocalypse just controls their minds.

In comic canon, Apocalypse recruited Angel to join the Four Horsemen as Death, along with three other mutants. They all soon returned to normal. Much later Apocalypse recruited four new Horsemen, including Caliban as Pestilence and Wolverine as Death.

Angel, Havok, and Boom Boom make their first season 4 debut. Spyke makes his second.

Apocalypse's plan to put the X-Gene to humans (which will kill them) is similar to Magneto's plan in the movies.

Though the tagline promised "[the return of] every character from the past, good and bad", several recurring characters were absent: Jubilee, Wolfsbane, Forge, Juggernaut, Sabretooth, Pyro, Gambit, Mastermind and X23 are unaccounted for. Similarly, none of the characters introduced this season (Omega Red, David Haller, Danielle Moonstar) make an appearance.

For the first time in this series, Apocalpyse speaks in this episode, when he speaks to Professor Xavier, and when he calls out his Four Horsemen.

The Teams are:
Team 1: Wolverine, Cyclops, Nightcrawler vs. Mystique
Team 2: Jean Grey, Boom-Boom, Colossus, Multiple, Magma vs. Professor X
Team 3: Beast, Berzerker, Iceman, Spike vs. Storm
Team 4: Shadowcat, Sunspot, Angel, Havok, Scarlet Witch vs. Magneto

Apocalypse now has armor like in the comics, and in the old TV series.