Quake 4 Easter Egg - Yugioh Gx in Quake 4

Two enemies in the game has quite high reference to the anime Yugioh GX from Japan. First enemy group is the Strogg Conscripts which are one of your first enemies in the game (machinegun, shotgun, nailgun Conscripts). Sometimes when they see you, they shout "Truesdale!", who is actually Zane Truesdale (or Syrus Truesdale), a character from the Yugioh GX series.

The second enemy is the Strogg Gunner. That tough guy with a nailgun and a grenade launcher, you will first see him in level "Hangar Perimeter". Sometimes when he sees you, he shouts "Aster Phoenix!" who is another character from Yugioh GX series. When the Strogg Gunner is away from you, you might not hear it clearly, but on level "Dispersal Facility",where many Strogg Gunners appear at close range, you may hear them shouting this.

Last but not least, one of your mates in Rhino Squad is called Rhodes, this might be a reference to a third Yugioh GX character, Alexis Rhodes. Although it'd not be an easter-egg alone, after the first two, I think this might be another one.