Poison Mushroom

Description
The poison Mushroom is a rare anomaly said to manifest if the player is blasting through level's with ease, oddly enough running away and avoiding 1-UP mushrooms have been reported to not be a factor of spawning the mushroom. the poison mushroom is said to be in boxes without indication of it's contents or sometimes out in the open. when opening a poison mushroom from a box it will chase Mario down until it catches up too him. when touching it instead of losing a life or even taking damage Mario will become dizzy. during this dizzy state Mario can lose up too 5 bars of health, although most reports have said that he takes 3 hit points. after around 6 too 8 seconds Mario will get back up on his feet and gameplay will return to normal. the poison mushroom is said to be in later levels of the game although it's said that it can appear on revisits to older levels.

Theorizing
Many people have said that the maker of the Lego Mario poison mushroom had a somewhat personalized copy as the LEGO variant of the mushroom also makes Mario dizzy for a couple of seconds. some have also used this to explain some other oddities in the sets like thwomp being in a lava themed set, although this claim is quite baseless as he's appeared in castle levels in multiple Mario games.

Trivia
Oddly enough the poison mushroom is one of the few anomalies that's said to be able to be found in the game files and even more peculiarly is said to be called PEACH120.DREAM instead of poison mushroom even though reports have said that it's been referred in game as the poison mushroom, although these reports are unconfirmed and could easily be false.