The "Weebeeka" Corruption

The Weebeeka Corruption is a debunked, common phenomenon related to Semantic Satiation, an auditory phenomenon where a word being repeated enough times causes it to lose meaning to the listener.

Explanation
The phenomenon is in relation to players noticing after playing for a while, that Mario's victory speech is completely incomprehensible gibberish. The first recorded case of this happening with Super Mario 64 was some time in 2002 by a person in Florida.

The explanation for it, is that it is a common auditory effect known as Semantic Satiation, a psychological phenomenon in which repetition causes a word or phrase to temporarily lose meaning for the listener.

Experiment
If you want to experience this for yourself, repeat Mario's "Here we go!" clip on loop for a while, if you don't focus on it, the voice will begin to change and you'll notice that it becomes gibberish.

You can also achieve the effect by playing Super Mario 64 for extended periods of time without paying attention to the sound design, eventually you MIGHT be able to hear it.

This phenomena is very easy to replicate due to it being so common in everyday life.