Leonard Rockstein, more commonly known as Dr. Rockzo (often misspelled "Rockso") is the "rock 'n' roll clown"; he does cocaine. He is quite possibly the heaviest drug abuser in Metalocalypse, and is addicted to many other drugs besides coke; in "Cleanzo", Dr. Rockzo admits that not only does he use cocaine, but he also huffs paint, and uses crystal meth, heroin, pain pills, and Oxycontin. In his words, "I do it all."

Dr. Rockzo is the trouble-making son of a physical therapist who became lead singer of Zazz Blammymatazz, a partying rock band named after the guitarist. They quickly became famous; however, Rockzo insisted on being paid in cocaine. His habit made him increasingly paranoid, and he was eventually fired from the group. After a short-lived solo career, he began his present life as a rock n' roll clown for hire. He was once briefly the star in a reality show, before stealing over 1,000 pounds of cocaine from a police storage facility and going into hiding. One of Dr. Rockzo's talents is constructing elaborate and large balloons in a matter of seconds. He has made a Bootsy Collins Space Bass guitar and a large balloon in the shape of Toki's face. He offers to make one for Nathan outside of a police station, which Nathan declines.

He talks in a high-pitched voice, which every member of the band except Toki finds irritating. He wears a very tight neon jumpsuit with cutouts that expose almost his entire torso and, in the back, the top of his buttcrack. The rest of his outfit includes a combination cap, long, thick, brightly-colored hair, KISS-like face paint, furry boots, and a spiky red nose. The colors of his clothing and hair change between episodes, but are always gaudy and fluorescent. Without the makeup, he is shown to be a balding Caucasian man with long blond hair.

Toki and Dr. Rockzo become friends following Rockzo's first appearance, as Toki has a childhood trust of clowns (he is shown as a child with clown/serial killer John Wayne Gacy). Rockzo is not well received by the other band members, particularly Murderface. Ultimately, Ofdensen throws Rockzo out of Mordhaus and orders a few Klokateers to "put the boots to him, medium style". After this, a more deranged Rockzo is approached by the Tribunal; they hire Dr. Rockzo to gather information about Dethklok from the inside. Rockzo succeeds in taking numerous pictures of Mordhaus, but is forced to flee when Ofdensen catches him opening a safe in the manager's office. Later, in "Cleanzo", Rockzo convinces Toki to take him in, with the other band members deciding to get rid of him by sending him to be rehabilitated by Rikki Kixx.

In Snakes N' Barrels II, Leonard Rockstein has been sober for two months and he now does speeches about sobriety in Rikki Kixx's rehabilitation center and dresses like a normal person, referring to his "Dr. Rockzo" persona as the source of his drug abuse and had to rid himself of it. He is chosen to host Rikki Kixx's SOBERTOWN USA No Drugs Allowed Sober Rock and Roll Show where in the middle of his opening speech he starts seeing hallucinations of his former self telling him to do drugs. He freaks out and nervously goes backstage where he sees a confiscated bag full of cocaine and cherry pie filled with pot, eventually forced by the hallucinations to take the drugs, relapsing back into Rockzo. After stealing a woman's black tights, he bursts onto the stage in slapdash clown makeup and hair, covered in cocaine and cherry pie sauce and screams in a dark tone, "MY NAME'S DOCTOR ROCKZO, THE ROCK AND ROLL CLOWN, AND I DO COCAINE!" Coinciding with other intense moments in the episode (such as Toki beating a man to death, and the members of Snakes 'n' Barrels suffering from severe aftereffects of Totally Awesome Sweet Alabama Liquid Snake), this was quite a climactic moment.

He makes his latest appearence in Season 3, in the first Metalocalypse Christmas episode, Dethmas. At the begining of the episode, it is revealed that Rockzo had been arrested for stealing Christmas presents to sell so he could buy cocaine. Toki reveals that he has cutoff all connection to Rockzo. Rockzo is let out of jail on parole & gets a job as a department store Santa. Toki is at the mall to meet Santa, only to meet up with Rockzo and brings him back to Mordhaus with him. Toki lets Rockzo use his shower to clean himself up. Rockzo tries to get Toki to get him some cocaine, but Toki refuses, causing Rockzo to violently push Toki's head into the bathwater—stopping short of drowning him. Left alone at Mordhaus while Dethklok goes shopping with their moms, Rockzo steals Toki's secret Santa presents and pawns them for money to buy cocaine. Rockzo later crashes Knubbler and Murderface's Christmas special, where he receives a handjob from a drunk Serveta Skwigelf. Toki discovers his presents gone and confronts the clown, threatening to kill him; however, a wooden cross falls on Toki, pinning his legs under it. The episode ends with Rockzo stating "Best Christmas Party Ever".

Rockzo seems to be a parody of various events and persons. During the beginning of the episode "Cleanzo," Dr. Rockzo is seen in his underwear struggling to eat a cheeseburger, a parody of an incident involving David Hasselhoff. Dr. Rockzo has also been said to be a parody of Van Halen frontman David Lee Roth (it is later stated in this article that he is a parody of Eddie Van Halen himself, but Roth fits the bill more accurately based on his behavior.)

A common running gag in the series is to have Rockzo repeatedly kicked by Klokateers. This happens in "Birthdayface" after he attempts to entertain Murderface, and in "Dethclown", when he gets kicked out of Mordhaus.

Known Dr. Rockzo songs Edit

Dr. Rockzo's signature song is most likely "I'm Just a Rock n' Roll Clown", which appears in two episodes. It describes Dr. Rockzo and his cocaine abuse. Later, when Rockzo becomes sober, he is shown performing a song called "Goodbye, Snowy Road", a soft power ballad about him leaving his life of cocaine and other drugs (the "snowy road" referring to cocaine). It is revealed that Rockzo is able to play piano. "Atomic Clown" and "Dory Mclean" appear in the episode "Dethzazz"

Trivia Edit

• Dr. Rockzo owns a Mauser C96 Shanxi Type 17.