I just came across some beta footage for ClayFighter 63 1/3. Take a look:
Vhs X64 La Video n64 1-1
(Footage starts at 15:40)
What I noticed different from the final game:
- Intro is slightly different.
- Lifebars are different. They seem to be unfinished, as they only show Blob and Frosty.
- Character select menu is different. The final characters are there except Jim and Santa, and Hobo Cop and Lady Liberty are there.
- Camera moves differently.
- Bad Mr. Frosty has two moves not in the final version. An Ice Breath-like move and a launcher with his "little buddy".
- Blob has a red alternate palette and a different at mercy animation.
- Bonker has his green palette not in the final game, and some different animations. He also appears to have a move involving his cannon.
- T-Hoppy has a grey alternate palette.
- Other changed character animations.
(Credit to DummyCorps on reddit for finding this)