Choice of Alexandria has an achievement “Choice of Robots.”
That’s the only one I am aware of. But, as I just put a small homage to Cannonfire Concerto in my own work in progress, I was curious whether there are any other easter eggs that you know about?
There are characters from Zombie Exodus that show up in Zombien.
Oh, neat! Yeah, that’s exactly the sort of thing I was wondering.
@Nocturnal_Stillness’s Hosted Game UnNatural has in-game joke ‘advertisements’ that are homages to a number of other Hosted Games by various authors, including Zombie Exodus and Life of a Wizard. Several of the media references in the game are also references to other games.
You’ve written Unnatural as UnNatural a few times now and I’ve now decided I like your version better.
Yeah UnNatural has several homages as both in-game adverts as part of the “TV show” theme.
Also Choice of a Vampire becomes a movie “Rise of a vampire” Zombie Exodus and Safe haven are a film series and Community College Hero is a video game the player can play in episode one.
Also Zombie Exodus has an UnNatural easter egg when you can find Jason playing the game on the PC
I know it’s only a WIP, but there are some CoG references in Monsters. 
In my WiP Choice of Rebels, the Xaos-Storms are caused by Hawkins from Mecha Ace.
See, I knew it. There’s just one big Choiceofverse, and we are just exploring small shards of it, little by little.
Maybe in 2020 we can publish one of those huge crossover type of stories involving time travel/dimensional portals/insert plot device here where the heroic NPCs of a few dozen games band together against the (surviving) antagonists of those same games in an epic money grab…oops I mean epic struggle for the fate of the universe…and the MC can tip the balance either way!
Zombie Exodus: Safe Haven has an Easter game in which you can play Apex Patrol: Lone Survivor, a full 4,000 word prequel to @AllenGies game.
like with Attack on Titan with DC & Transformers with Marvel & Generator Rex with Ben 10 and…
yeah, I’m going to stop there before someone sends in Deadpool and Deathstroke-
“Stan-Lee!George Perez!Marv Wolfman! I have a new Marvel crossover with DC idea for you three!”
(and I am killed)
So I should put a strange, unexplained door in my game, and then we simply find a way to turn that into a portal into another game, and so on.
Which of course leads to the most important question of all.
Which protagonists from which CoG/HG games might be able to survive–and thrive–in the most other games?
Well, if I ever find the energy to do a sequel to Apex Patrol, I’ll have a chance to find out all about cross-overs after I introduce the Quantum-Simulator (Holodeck) to the ship. No genre or character will be safe. And it’ll be hell to write.
For the survive/thrive matrix we’re about to construct, why don’t we consider a few ground rules.
First of all, I’d like to propose that any powers or abilities the crossover protagonist has in their universe remains active in the new one. It feels boring to say… ‘But since there is no magic/zombies/trombones in this reality…’
Two, I suggest that the crossover protagonist (CP?) is allowed an initial safe zone and some time to acclimate.
Three, it is late and I’m off to sleep.
I don’t know if anyone still cares characters from the Orpheus Ruse show up in MetaHuman Inc both games are by the same author.
I still care, Avidreader. I still care.
It’s been confirmed that the Aguilar Baylock duels in the middle of Guns of Infinity is supposed to be a reference to Choice of Romance.
(I didn’t notice the duels were references though haha.)
I think I threw in a line in CCH Part 2 where the MC is brainstorming some outlandish ideas to make the MC more powerful, and one of the discarded ideas is, “somehow eliminate my enemies by stealing their powers and absorbing their memories!” as a shout-out to Versus.