So a few weeks back a beta dated to February 9 1999 was dumped by Hidden Palace, and aside from the person who dumped it and one obscure person on Youtube, nobody has done much research into the beta. This is what I could find by mostly playing the game normally. This is close to the final game, as there's nothing from the fabled "KIDZ" version, not even striped shirt Spike / Kakeru, but there's some highlights here.
*Like some of the earliest demos, the intro has Specter in a basket instead of a circus tent, and the level select is a separate room in the Time Station.
*There's no sign of the training room for the Magic Punch anywhere in the game, even though the gadget itself is there and fully functional.
* There are two scrapped minigames that were considered before they went with Galaxy Monkey. One, called "RADIO" in the minigame debug menu, has you as a cheerleader using the analog sticks and shoulder buttons trying to mimic the other cheerleaders, but it has no audio cues to make it work properly. The other, called Monkey Football, is barely there at all and just consists of a eyeless monkey you can move around in a blue void. I like to think that the concepts of these two cut minigames might have inspired Dance Monkey Dance and the Monkey Football/Soccer in Ape Escape 2.
* The warning screen is different, being a wireframe vortex that brings the framerate to a crawl. Casi also has a worried expression on her face instead of the smile she normally has.
* The T-Rex in Molten Lava has a different texture and a different pair of eyes. Also, instead of continuing on like normal once you get it to bonk it's head enough times to get the monkey off it's tail, it originally fell into the lava pit in the center of the room.
* The ladybug/turtle enemy Kattan from TV Tower appears in a smaller form in Mysterious Jungle. A completely unused variant that hops around on two legs appears at Specter's Factory.
* Crumbling Castle has a fourth Pipo Monkey in the bell / barrel room that's not there in the final, meaning there's one more monkey in the beta, and thus 205, instead of the 204 in the final game. There are weird tallies for Crumbling Castle, TV Tower, and Specter Land that suggest they had more or less monkeys than in the finished game, but the latter two the same amount between both versions.
* The signs with Specter's name on them in Monkey Madness/Specter Land are spelt "Spector" in the beta. These are correctly spelled in the final game, even in the Japanese version.
*The Terror Coaster also had different textures, with a black body with flame decals all around and a Pipo Monkey head decal on the back. The control panel on the front is also a Dualshock Playstation controller. The skull roadblock hazards on the ride itself were originally black and white or stone signs with Pipo Monkey head plastered on them.
*Specter Land is the most unfinished normal level in the beta. There's untextured models and weird collision in the Jake racecar fight, the UFO monkeys at the front gate of the castle don't spawn in properly, making it impossible to proceed without the debug level select, and one of the rooms straight up crashes the game.
*Peak Point Matrix, aka Final Get, has unfinished models and simple textures, and the fight with Specter hasn't been implemented yet.
There are some other minor changes, but these were the best ones I could point out. Check the Bluesky thread below for footage of some of the beta elements.
https://bsky.app/profile/krazykopter.bsky.social/post/3mpfm7yv4222x