Psycho is insane, which is characterized by his pale blue eyes with yellow and white swirls. He wears an unbuckled straitjacket, implying that he has spent time in an asylum. His weapon of choice is a straight razor (which he never actually uses; however, at the bar, he is seen threatening Eddie Valiant with it, but to no avail). He has spiky, unkempt fur by the hairline, and is the only member of the Toon Patrol who does not wear a hat.
Psycho seems to be an overall happy character, even with his mental condition, as he is usually shown grinning and laughs more frequently than the other weasels. He apparently gets excited by the concept of killing, as he is heard gleefully laughing when his boss Judge Doom kills the Toon Shoe in the bucket of Dip. He nearly drools in anticipation as his boss Smarty attempts to drive Benny the Cab, and he takes it upon himself to shoot the Dip at Roger and Jessica. On a few occasions, it is implied that he enjoys pretending his straitjacket is buckled by hugging himself tightly, namely when he exits the Toon Patrol's car in his first appearance, and while laughing after Eddie stuffs a bar of soap into Smarty's mouth. Psycho has a shrilling laugh and high-pitched voice.
Psycho only has two lines in the film; he first speaks when he says, "Time to kill the rabbit." as he prepares to shoot Dip at Roger and Jessica, and when he says, "Bye-bye." after he dies. Psycho is the last weasel to die, not only by losing control of his laughter, but also by losing his footing and falling on the giant rotating brush of the Dip machine, which flattens his body. He manages to remain a threat even after his death; as his soul rises out of the warehouse, he turns the pressurized Dip spray back at Roger and Jessica.
When Psycho says, "Time to kill the rabbit," his dialogue is loosely similar to the line of Fred the donut maker from Dunkin' Donuts who says, "Time to make the donuts."
It is possible that when Psycho fell on the Dip's brush, flattening his body, the Dip drenched on the brush might have killed him without completely destroying him, or he probably just died from laughter on the way down. However, it wasn't quite clear, though the latter fate is more likely since his ghost appeared.