Smilers are generally hostile, and there have been many confirmed sightings of them. They can be identified by their signature reflective eyes and teeth gleaming in the dark. The best way to escape a Smiler is to keep eye contact. Smilers tend to reside in dark areas on Level 2 and Level 3. Their Base is known to be "The Smiling Room".
The Smiler is attracted to light, and will chase anything they see with a light, so distracting it by throwing a light source at it would be great for an escape. The Entity will only start to attack if you panic and retreat, or if a loud noise is made. Keep eye contact, and move away slowly to ensure your survival. Using a Smiler Exterminator will cause the Entity to retreat or lose its senses for a long period of time.
Smilers have a long smile with multiple sharp teeth, and have white glowing eyes; It is unknown what else it has for its biology, though it is rumored to have a physical body, which cannot be seen with the human eye. It's rumored they have non-human, alien-like bodies, with arms and legs bent in unnatural ways, but this is unconfirmed. The M.E.G. is currently trying to find out more about its biology at the moment.