The Forest Carnival is accessible through the white dresser in the Forest Carnival (Interior).
Features
The white dresser will lead you to a dressing room, with the portal being one of four identical white dressers, except they do not serve any purpose. Exit this tent, and you will be brought to an enclosed field filled with blue flowers, with two other tents to the right of the one with the dressers. You can also find a sign with a clown on it, possibly advertising the carnival. If you step over the clown's face, the sign will tear and you will fall down to the underground part of the Laboratory.
In the first tent to your left, you will meet a man wearing a fez, who appears to be the carnival's ringmaster. He does not interact with you, and if you kill him, his fez will remain in the spot you killed him. However, his death is not permanent.
In the second and last tent to your left, you will come across what appears to be a woman sleeping, covered up by a blanket. She could be one of the carnival's entertainers, or simply someone seeking shelter. (The tent is filled with crates, and appears to be used for storage needs.) However, when you leave the tent and come back, you will find the same woman with a knife in her back, covered with blood. Like the ringmaster, her death is not permanent.
It is also important to note that you can see the interior of the other tents from corners of the others. So, when you exit the tent that the woman is in, and enter the ringmaster's tent, you are able to view her corpse this way. This means that the woman is killed as soon as you leave the tent she was in, and not when you come back.
As of 0.099e, the woman's hair is now black and she is not killed when you exit the tent she is in.