- Moral Event Horizon: Professor Burnital crossed it by causing the machine to malfunction and destroy Midway, killing everyone on the planet aside from Muto, Al, and Janky.
- Nightmare Fuel: The Charks in level two.
- That One Level: There are a lot of annoying levels in Dr. Muto, but the Furnaces take the cake. Gone are the fun flying sections of the first two Flotos parts. Instead, you're forced to endure a seemingly endless course of infuriating jumping segments. The "highlights" include using High-Jump Boots to navigate columns of spinning platforms, the infamous rafter section, and killing a bunch of durable enemies while on a time limit. By far the worst part is the rafters, where you have to navigate a long gauntlet of completely unfair obstacles, while as the hard-to-control Mouse (or Rat), and with barely any checkpoints when you need them. Just getting to the place is annoying enough, since you have to traverse a giant broken wire with electric balls bouncing down it, and a mess of steam jets, every time you go in and out of the place. The worst part is, it locks you in the area until you complete it, and there are no save points there to escape (and restarting will send you right outside the rafter entrance). And you don't get to fly again until halfway through Jupiter City, the next section.
YMMV / Dr. Muto