"Junior" Max

Throughout The Devil's Playhouse, Max demonstrates psychic powers that build as the episodes carry on. However, by the end, his psychic powers get out of hand and ultimately transform him into the monstrous "Junior" Max.

Beyond the Alley of the Dolls
As the plot unfolds, Max fights Charlie Ho-Tep who is attempting to summon the Lovecraftian horror Junior into this world, an act that would result in the destruction of everything. Although defeated, Yog-Soggoth unlocks Max's full psychic powers so that Max can defeat the demonic dummy. Max succeeds in defeating Charlie Ho-Tep and stopping Junior's return. However, he lands in the remnants of Junior and accidently consumes the bits of the elder god. This leads to the transformation into the Junior-like monstrosity much to Sam's horror.

The City That Dares Not Sleep
Max, now as a mindless and destructive eldritch abomination, proceeds to rampage through New York City. Sam and his team of the pregnant Sybil and Anton Papierwaite with Yog-Soggoth enter Max's body in the guise of a corn dog and seek to reverse his condition. It is discovered that Max's sudden transformation is caused by an overload of his psychic powers building up as a deadly tumor in his brain. (Although the consumption of Junior would explain the outward appearance.) Despite gaining control of "Junior" Max's arms and legs, the transformed lagomorph continues to cause more destruction.

Sam discovers that the Narrator is the culprit behind Max's demonic state. The Narrator, being a manifestation of Max's long-suppresed superego, seeks to destroy Max by turning him into a ticking psychic energy bomb. However, he sees the error of his ways once seeing the Max spores acting together to save Sybil when her water breaks, convincing him that Max is worth saving. Unfortunately, as Sam and his allies escape, "Junior" Max is hit by a warhead. Unable to allow this to destroy New York City, he tearfully waves goodbye to Sam and teleports away.

Max is seen teleporting aboard the ship of the fleeing General Skun-ka'pe and the resulting explosion kills all onboard. Following Max's demise, a past incarnation of the lagomorph appears in a time machine and essentially takes his place.

Max Spores
In addition to the destruction caused by the Lovecraftian horror Max, there are also a series of spores manifested as floating Max heads set aflame. They feed on the psychic energy produced by dreaming and thus go out trying to force everyone in New York to fall asleep so they can feed the host ("Junior" Max). They also tend to be pretty hostile in their own right, not unlike Max prior to his corruption, and threaten/insult Sam and company during their time inside the body.

According to a newspaper seen in-game, the demonic Max's rampage went on for at least two weeks prior to the beginning of the game. The headline encourages New Yorkers to remain awake so they can avoid becoming victims of the feeding. This is punctuated by a Max spore floating directly at the camera in the beginning, telling the player to go to sleep.