Well, way back in chapter 1, I added in this meme when it was relevant
Emerald has a poster of Super Saiyan 2 gohan in her living room
The guy that Isham was caught draining the blood of falls in the Peter Griffin pose
Not really much of an Easter egg, I just wanted to plan out that Emerald's mailboxe is shaped like a pelican
Just outside of the restaurant that Isham and Emerald have their dinner at during their first date is the temple of heat, and on it has the first depiction of any of the gods in the story in statue form.
A recreation of American Gothic
This guy in the crowd at the stunt show is wearing a sonic adventure two T-shirt
This proposal is actually between two characters in the background that will be significant way, way later.
also right next to them is someone wearing an imagination Institute (from journey into imagination with figment from Epcot) T-shirt
The pineapple on the hilt of Esen-Ali's sword is the first hint that she is an angel (this is a joke on how apples are the fruit that represent demons, so Argo, pineapples must represent angels)
Humanized versions of tangle the lemur and whisper the wolf in this flashback crowd scene
Again, this isn't much of an Easter egg, I just want to point out some of the things that are happening in the Crossview section of the hospital scene that a lot of people might miss
A herd of wild imps is seen to foreshadow Kno's pet imp
Emerald has a Pikmin shirt as she is leaving the hospital
Sisyphus in Hell
The background behind Lolly here is a rather infamous piece of modern art known as
Who's Afraid of Red, Yellow and Blue
I don't know what this is called, but this was seen in one of the adventure Time episodes taking place in the nightosphere, only in adventure time it was kind of like a bus, I made it kind of grosser
If you know anything about Pokémon, you will know why Absol appearing on Emerald's sweater is forboading.
The flying boar appears in between on top of the panel where Isham is talking about avatar the last Airbender, specifically The Swamp