This easter egg is referring to the game StarCraft 2 by Blizzard. There are three fractions in StarCraft 2: Protoss, Terran and Zerg. Imagine the Zerg like aliens. Zergs have a unit called "the Zergling" which is a small creature that usually attacks buildings and enemy units in groups. If you have a lot of Zerglings and run to your opponents fast this can be called "a Zergling rush". There are also custom maps that…
Well, I would say that it refers to the Starcraft series. I'm so old that I remember the first Starcraft game – and I'm quite sure it had Zerg. ;)
I remember when Dune 2 came out - the father of all RTS games.