Hey there, Kristen!
Thanks for bringing another great question to the Disney Parks Moms Panel. Every trip I notice details left by Disney Imagineers that were waiting to be discovered, and I have made it my mission to really stop and explore as many details as possible around the
Disneyland Resort.
You could probably write a large book about every hidden detail or "Easter egg" in both parks! I know I have barely scratched the surface, but I will tell you some of my favorites. Over in Critter Country, apart from Max, Buff, and Melvin, you can see many nods to the Country Bear Jamboree attraction that used to exist here. Look at the restroom signs at the Hungry Bear Restaurant, the art in Pooh Corner, and "Sammy's Recycalatin' Corner" near the exit of Splash Mountain for Characters from this classic show. Speaking of Splash Mountain, almost all of the Audio Animatronics you see on this attraction were actually taken from the retired America Sings attraction that used to exist in Tomorrowland. This attraction closed in 1988, but thankfully the many critters found a new home!
The 1955 Golden Book "Little Man of Disneyland" tells the story about a leprechaun who lives on the site of Disneyland as it is being built. When in Adventureland, take a look at a tree near Indiana Jones Adventure to find this little man's house still standing today.
Finally if you have some free time, I suggest looking at all of the signs and windows on Main Street, U.S.A. While some of the names in the windows are quite obvious tributes, others are fun to research if you haven't heard of them before. Also, if you like hidden Mickeys, check out my favorite one inside the "Ice Cream Floats" lettering in Gibson Girl Ice Cream Parlor's window art.
Like me, I hope this helps you appreciate even more of the hard work that has gone into making the Disneyland Resort so special and magical.
-Jennifer