There is a "classic" Doctor Who episode called "The Call of Kroll", where the Doctor and his companion fight this giant giant squid (That's a giant squid that was made giant ), called Kroll. So here's the Easter egg: It looks just like the death spell Call of Khrulhu.
Khrulhu is KI's Cthulu. The same goes for Blizzard. Blizzard made C'Thun as their Cthulu. Terraria has the Eye of Cthulu and the Brain of Cthulu. I am sure the Doctor Who reference is just a coincidence.
Also, speaking of easter eggs. In Khrysalis in Tyrian Gorge, there is a bug named Zur'Grush. This sounds like 'zerg rush', which is a Starcraft thing.
