Yoshi’s Island is one of my all-time favorite video games, one reaching a platforming perfection few games, including its “sequels”, have been able to recapture. So it would make sense that it’s one of few I played enough to discover a glitch: this glitch, which I submitted looong ago to a Mario fansite I used to frequent.
As a note, the fan’s video above doesn’t demonstrate the glitch quite right. If you knock the shell away, the half-naked Koopa will continue to march back and forth in place inside of the hill, making it more than a slight visual glitch.
Nothing says loving a game like finding its glitches. I learned some more severe ones for this game during AGDQ earlier this year, which of course were due to much less likely circumstances a typical player would never encounter within the game. One of my personal favorites is a glitch that involves eating Baby Mario, which of course makes the level impassable AND creates a time paradox.