Missing sprite from Aquatic ruin zone
missing turtle crawling animation.
Actually, it's not missing, but its a pain in the ass to view in the game. You must hit a badnik when you pass the wing fortress in Sky Chase Zone, so the turtle can fall on it and crawl away.
Balkiry with landing/takeoff gear
Bigass laser, from Wing Fortress Zone
Hidden Palace Zone stage select icon
random platform made of rings, moves back and forth depending where you stand.
Odd badnik? it sits in one spot, does nothing, but hurts you if you touch it. And if you destroy it, an animal comes out. It appears in Wing Fortress Zone.
Here's the weird ass SOB in person.
Download a video of it in action here