Neuron Flies provide 1 food pip (1/4 of a pip as Hunter and Artificer) when consumed and grant Slugcat the ability to glow for the rest of the campaign, providing visibility in dark regions. They can also be stored in Slugcat's stomach when all of their food pips are filled.

After eating a Neuron Fly, Void Spawn appear near Slugcat in certain locations. They are trapped in small 'eggs', and upon touch, they break free and slowly travel in a direction that leads from Shoreline Looks to the Moon to Shaded Citadel Memory Crypts, guiding Slugcat in the direction of Five Pebbles in place of the Yellow Overseer.

Hunter starts the game carrying a unique green Neuron Fly. This Neuron Fly cannot be eaten and can be stored in Slugcat's stomach at any time. If it lies on the ground for a few seconds, it starts hovering above the ground at the level of Slugcat's head and occasionally projects a complex hologram from its form.

When the green Neuron Fly is brought to Looks to the Moon, who is initially exhaustively incapacitated when Slugcat meets her, the green Neuron Fly reactivates her own Neuron Flies and brings her back to life. This is because the Neuron Fly holds 'slag keys'. Looks to the Moon became incapacitated because Five Pebbles deprived her of water, causing slag buildup which caused her processes to seize. The slag keys likely reactivated her water systems to flush out the slag and allowed her to become active again.

Fighting an Inspector can be challenging, especially when encountered in zero-gravity environments. Though their main body does not move quickly, this low speed is offset by the dexterity of their heads. Attacking one up close is risky, as Inspectors grab and throw any objects within their reach, including objects held by Slugcat, any Spears stuck in their tendrils, and Slugcat themself. Attacking from too far away, however, becomes impossible, as past a certain distance thrown Spears lose velocity and become harmless.

An Inspector can be killed by attacking their core, necks, or heads. Hitting their heads or necks with standard Spears or Rocks consistently deals 0.12 damage, which kills an Inspector in 8 hits. Since both deal the same damage, Rocks are the safer option, as Spears can be grabbed by the Inspector and used against their attacker. It can be helpful to hide extra Spears from the Inspector's sight before provoking them to prevent the Inspector from using them.

Most attacks on the core do no damage but have a very low chance to kill in one blow (0.1%). As such, focusing on the core with standard weapons is not a consistent strategy. However, explosives to the core are always lethal. It can be easier to use Explosives from further away, as an Inspector's necks can block a shot to the core.

It is possible for Artificer to stun and maul an Inspector, killing them instantly. This method is relatively safe, since deflecting near an Inspector does not provoke them, but it can be challenging to grab them in time due to the zero or low gravity environment they usually inhabit. Artificer is also prone to overheat from use of their Explosive Jump for both mobility and combat.

Although their attacks are fast, Inspectors are rather slow, making them easy to outrun. They can pursue the Slugcat between rooms but lose interest if the room's pipe is too far away or inaccessible.

Inspectors are initially passive, roaming through the zero-gravity environment. The fibers trailing on their bodies may reach out and contact fibers in the environment, lighting up blue at the ends.

Upon being approached, they use their tendrils to probe and feel Slugcat; this is harmless and has no effect on Slugcat.

If passive, Inspectors attempt to save Slugcat from stationary hazards, such as Proto Long Legs and flux condensors, by grabbing and throwing Slugcat away from them.

Inspectors become aggressive if attacked or if the Slugcat grabs or attacks Neuron Flies in their presence. They flash between red and white when angered. The state entered by grabbing a Neuron Fly is different to that of eating one or directly attacking an Inspector. Instead of trying to kill Slugcat, Inspectors pick up and drop items as if in warning and attempt to dislodge the Neuron Fly from Slugcat's grasp, becoming passive once it is released.

Directly attacking an Inspector or eating a Neuron Fly within their line of sight makes them aggressive for the rest of the cycle.