Images of Gotoh Hitori, aka Bocchi, where she's depicted as drawn noticeably worse, in a distinctly different style, or transforming into something completely different as a result of stress or anxiety.
Comes from a recurring gag in the anime, where Bocchi does exactly this when she feels anxious or stressed.
To qualify, it should be clear that this is not just the image depicting her in a different state, but it's a change or difference for Bocchi specifically - which means that most images in this pool will either have multiple characters or be part of a series. References to art-shifts from the anime can count, but Gotoh Hitori (octopus) and Gotoh Hitori (tsuchinoko) images should only count if the style (lineart, shading, etc.) is significantly different from the rest of the image or the normal, or human Hitori clearly transforms into them.