Penta Penguin, a secret character that can be unlocked via a cheat code, was unfinished in the North American release.

One example is one of his power-ups that shows an Uka Uka icon but when activating it, summons protection from Aku Aku; leading to some confusion of whether he's good or evil.

Another example has to do with his voice. Some of the voices are simply sounds Penguins make, but there are two samples that sound more like that of a human talking. This is actually incomplete code that was meant to be removed from the game. The samples are a male (possibly a voice actor or the audio engineer) reading the file names "Penguin Yay 1" and "Penguin Yay 2". This was fixed in the European release.
Contributed by HolySka1991