These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Literal ones in "Reptiles". These come in huge numbers, fire loads of spreadshots, and have a very good amount of health. Worse still, they swing about, causing easy Collision Damage. And there's also a giant tortoise to annoy you when you face them.
The rockets in "Catastrophe". An instance of Bullet Hell considering your large hitbox, these come in large numbers and shoot an 8-way spread of shots very often. If you don't eat them and their shots, your eater will get overwhelmed.
Fridge Brilliance: Using your "eat" move on the nuclear reactor boss gives you the Cancer ability. Remember what nuclear radiation causes in oragnic creatures?