Skeeter

Skeeters are spider-like enemies in Mario 64. They appear in Wet-Dry World (whose painting is an image of one) and Dire, Dire Docks in the DS remake, floating on water. They are blue water striders (also known as Jesus bugs) with an antenna leading to a red sphere and yellow feet. They deal damage upon contact with Mario, and are defeated by being jumped on.

They appear to be aquatic versions of the Scuttlebug.

Enemy Discoloring
Main Article: Enemy Discoloring

Depressed Skeeters
Main Article: Depressed Skeeters

Spider Skeeter Anomaly
Main Article: Spider Skeeter Anomaly

Empathetic Emotional Aura
While Wet-Dry World is most well known for it's Negative Emotional Aura, another aspect of the level often overlooked is the odd emotional aura exuded by the Skeeters themselves. Most players have reported feeling a sense of pity or empathy for the enemies, this is doubly so for their anomalous counterpart the Depressed Skeeter.

Skeeters also appear in a commonly Shared Nightmare involving them drowning in an even more flooded version of Wet-Dry World. The reason for this supposed Empathetic Emotional Aura is unknown, but the commonly accepted answer is that it is simply the player projecting their feelings about Wet-Dry World onto the enemies, feeling sorry that they must live in said enviorment.

This makes it very unlikely that the Empathetic Emotional Aura exuded by the Skeeters is anomalous in any meaningful way.