quick lore drop here, didn't have time to add this in the game, the rats are actually all hired by SperDuperSafe, to attempt to diffuse the companies bombs, and they've been so good at it
the ones that are glowing are the "Mechanical rats" made by SuperDuperSafe to replace the hired rats with robots, but instead of doing damage, they just add 5 seconds of time, because they're less good at their job!