Things on the internet make me happy

Early model of a Chain Chomp found in development files for Super Mario 64.

In Yoshi’s Island, the boss of Level 5-4 is Sluggy the Unshaven, a giant jelly-like slug creature that must be defeated by throwing eggs at it to deform it, allowing the eggs to hit its heart.

Usually, after hitting Sluggy with eggs enough times, the shape of the indention will automatically funnel the eggs towards the heart, dealing a hit, which restores the shape of the boss. However, with extremely precise and quick aiming, it is possible to aim the eggs so that they do not hit the heart and instead continue to indent Sluggy even further. This can eventually result in the indention becoming so deep that it goes all the way through, allowing Yoshi to pass through Sluggy and end up on the other side as seen in the footage. Note that this was not intended by the game, as seen by the spots on Sluggy’s back becoming glitched near the end of the process.

As the only way to replenish eggs in on the left side of the arena and Yoshi is unable to pass through Sluggy’s back, doing this traps Yoshi with no way of escape.

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