Like many of the Toys of Power of the Devil's Toybox, Charlie was brought from the Dark Dimension by Yog-Soggoth in order to entertain his eldritch abomination grandson Junior. Charlie possessed the power to throw the user's voice into anything and at full psychic capacity, the ability to project anyone's voice. However, due to its creepy nature, Charlie was shunned by Junior.
Charlie first appears in the second episode The Tomb of Sammun-Mak. In the reels showing the exploits of Sam and Max's ancestors Sameth and Maximus as they investigate the tomb on behalf of Anton Papierwaite, Charlie was in the possession of a mole girl believing him to be a perfect boyfriend substitute. Sameth and Maximus manage to get Charlie away from her and use its voice projection abilities to divert harm from them. Later, when Papierwaite attempted to force Maximus to summon Yog-Soggoth, Maximus used Charlie to trick Papierwaite into being victimized by his (unsuccessful) summoning.
Beyond the Alley of the Dolls
In the fourth episode, mysterious clones of Sam appear all over New York, prompting the duo to investigate. Their path leads to a cloning facility producing the Sam clones in sheer numbers to further their search for the Toys of Power, including the toy robot-esque Cthonic Destroyer capable of destroying anything from the Dark Dimension. Helped by a reformed Yog-Soggoth bound to Papierwaite, Sam and Max find the Cthonic Destroyer. They later also find Charlie at the dock and use the dummy's ability to divert the Sam clones. However, Charlie reveals itself and orders the Sam clones to subdue the two and take all the Toys of Power into the Devil's Toybox.
Atop a corrupted Statue of Liberty, Charlie plays on a piano containing demonic sheet music of the Dark Dimension and having Sam enthralled by his side. Charlie reveals his intention to summon Junior into Sam and Max's world to regain his favor, as the warped toy's desire is to be played with once more. He intends to accomplish this through the mass sacrifice of the Sam clones (Sam being the perfect base for the clones due to his "easily malleable brain"). He also intends to utterly destroy everyone and everything in their world in the process, getting giddy at the chaos to follow Junior's return. Insulted by the captured Yog-Soggoth/Papierwaite, Charlie attacks them with the Cthonic Destroyer. Sam manages to change the music enough to adapt the Statue's now-demonic features to allow Max to get up there. However, Charlie catches on and flings away the Cthonic Destroyer.
Yog-Soggoth unlocks Max's full psychic potential which allows the lagomorph to engage the dummy in battle. He is initially unsuccessful when Charlie assumes the form of the Cthonic Destroyer and deflects his attacks. Using a facsimile of Charlie to make Yog-Soggoth's insults emit from the Devil's Toybox, Max tricks Charlie into destroying the Devil's Toybox and all its contents. Realizing this too late, Charlie screams for Junior to play with him as he is destroyed with the rest of the Toys.