This is EXTREMELY interesting to me for a couple of reasons.
The eggs in this prototype are purple, and does not have any sounds associated with it.
At 0:04, Bamboo Terrace's theme does not have that singing in the final version of the game.
At 0:47, in Sunny Villas' skateboarding level, it plays Spooky Swamps' theme.
At 1:40, in Icy Peaks' egg thief level, it plays Spooky Swamps' theme.
At 2:56, in Agent 9's Lab, when you shoot the Rhynoc to kill them, they do not make any noise.
At 3:14, Sgt. Byrds' theme has different instrumentation. Sounds more bass-y, and is missing some instrumentation.
At 3:36, the hummingbird's name in Sgt. Byrd's Base is Eric, suggesting that one point, the hummingbirds were supposed to be male.
The egg names might be different. For example, at 3:58, the egg's name is Lockford, whereas in the final version, it's Ruby.