Christian Barnes, who is accused of being responsible for two dry-ice bomb blasts, entered his plea via a videotape arraignment from his cell at Orange County Jail.
Several family members were on hand for the video court appearance, but only his grandmother would talk with reporters.
"He's the nicest person I know," said Flora Barnes.
"He's a wonderful kid," she said. "He's a kid who wouldn't hurt anyone.
Barnes appeared briefly during the arraignment, his hands stuffed in the pockets of his orange jail-issue jumpsuit.
He was ordered held on $500,000, half of his original bail.
The Orange County district attorney's office says the first dry-ice explosion took place about 4 p.m. Tuesday outside Toontown shortly after Barnes was ending his shift and a colleague was taking over the vending cart with drinks.
Several minutes later, Barnes is accused of taking a second water bottle from the cart and walking toward the employee break room. While passing through Toontown, Barnes allegedly placed a second water bottle with dry ice in a trash can before leaving the area.
No one was seriously hurt in either blast, although authorities said some people complained about ringing in their ears.
Nonetheless, the explosions caused anxious moments in Toontown, which features Roger Rabbit's Car Toon Spin and other attractions aimed at youngsters.
"Barnes is cooperating with investigators and has indicated this is an isolated incident with unanticipated impacts," Anaheim Police Sgt. Bob Dunn said after the arrest Wednesday morning.