Still reading through everything but here goes...
-At HM, when you're waiting to get in, there are the tombs with funny sayings on them. One of the tombs has eyes which blink and open every so often. You have to watch it closely.
-When they originally tested Mission Space, it was more intense than it is now. People were getting off the ride and losing their lunch so they toned it down to what it is now.
-When Mission Space originally opened there was no Orange and Green side. It was all the same.
-The 2nd story of the buildings on Main St are all made smaller than the first story to give the impression they are bigger than they are (forced perspective).
-The only building NOT made like this is to the right as you walk into MK. This was because, if it was made that way, you'd be able to see (I believe) the Contemporary and it would ruin the feeling.
-You can view the fireworks for MK at the California Grill at the Contemporary. Don't have to eat there, just walk out to the observation deck. They play the music and everything.
-Sometimes, if you get a chance to ride in the front of the Monorail, you'll get a license. I have one as does my oldest son.
-In Tomorrowland there is a talking trash can. Or used to be. Haven't looked for it in a while.
-In MGM (sorry, still call it that), by the Indiana Jones Stunt Spectacular, there's a well with a rope going down into it (right near Gertie the dinosaur). If you pull it, you'll hear someone down there.
-When walking down Main St, take the first right (near the fruit stand). Upstairs on the left is a dancing/singing school. If you hang out you'll hear them playing scales and dancing.
-In
Disneyland (not sure if they changed this, been a while), if you look upstairs near the castle (on the back). Can't remember exactly which window but the witch from Snow White opens the curtains every so often to look down on everyone.
That's all I've got for now. Will think of more. Sorry for any duplicates.