U-5, also nicknamed as the "Chesire",[1] is the first entity the player will encounter in April Fools 2023 version of Section U. Like other Section U entities, it will rush to the last room at a slow speed.

Unlike most Entities in the game, U-5 does not have a light, and also does not shake the screen, so is only noticeable from its laughing sound, U-5 is a smiling face with white eyes and red teeth, and its mouth is from Smile Dog's creepypasta, the entire face is SCP 087 - B, which is also us