Anomalous Mario Manifestations

Anomalous Mario Manifestations are anomalous instances where the Personalization A.I., or potentially corruption, replaces objects with the Mario model, even if they are fitting or not. This is not to be confused with the Mario-Bowser Fusion anomaly, though the Mario-Bowser Fusion may be an incomplete manifestation of an Anomalous Mario Manifestation due to their similar nature.

Behavior
The most common form of Anomalous Mario Manifestations are enemies such as Goombas being replaced with parts of Mario's model in order to correspond to the enemy's body parts, though some have simply reported the head or singular parts being replaced with the corresponding part of Mario. These enemies do not appear to change behaviors.

Some more extreme forms of Anomalous Mario Manifestations replace enemy models entirely with the Mario model instead of the parts of the enemy being replaced with Mario parts. These instances of Mario have also been reported to use Mario's voice and sounds, making it hard to distinguish which enemy the Mario has replaced excluding the behavior.

The final form of Anomalous Mario Manifestations reportedly replace regular objects such as trees, part of a level, or making the entire level into a large Mario model, with or without matching collision. Some have reported the title screen with Mario's head becoming a playable level, and it is believed this is an instance of Anomalous Mario Manifestations, though it may be a separate anomaly entirely as this form of the anomaly is rarely reported.

Something worth noting is that this anomaly appears to occur the most on March 10th, which is known as Mario Day due to the date spelling out MAR10, implying a connection to the Internal Clock anomaly, though several people have reported the Anomalous Mario Manifestations appearing on Mario Day without the Internal Clock anomaly being present, though some believe it may actually be present but goes unnoticed.

Theorizing
The most common theory about Anomalous Mario Manifestations is that it is caused by the game or personalization A.I. being corrupted and accidentally begins to replace models with Mario's model, though why this occurs with Mario's in particular and not other models is unclear. Another theory is that it was intentional, and designed by Nintendo alongside the Internal Clock as a special feature for Mario Day, though this is unconfirmed.