At the beginning of the movie, the other characters believe that he doesn't have any powers. It is only at the ending of the movie when they're displayed: distraught at being forcibly taken away from his mother, an infant Jack-Jack lashes out at a surprised Syndrome, who had kidnapped him, first by setting himself on fire, then becoming a lead weight, and finally a small devilish creature. Pixar also created the short film, Jack-Jack Attack that shows Jack-Jack discovering his powers while unleashing horror on his babysitter, Kari Mckeen.

Jack-Jack normally communicates with subtle gestures and facial expressions. He usually speaks baby gibberish and can barely speak in human form—he only did so three times in the movie: first, when Lucius Best ( Frozone) rang the doorbell to the Parrs' home (he says "Hello?"), the second, during his confrontation with Syndrome; he threatened in his many transformations (most notably his monster form) to kill the villain, all while throwing a tantrum he cries "Jack-Jack down!" the infant fought and scrambled down Syndrome's leg. And third, at the end when Helen rescued Jack-Jack after being dropped by Syndrome (he coos, "Mama!").

Powers

Even though he is an infant, Jack-Jack has developed numerous super powers. How much control he has over the these powers is unknown, they may possibly be triggered by the situation as after he saw a picture of a campfire was when he first immolated himself, much to the shock of his babysitter Kari. His powers awakened during his time with the babysitter when she started playing Mozart music.

Some of his powers include

• Levitation/ Flying
• Shape-Shifting (Jack-Jack can change his form into fire, metal, or a monstrous demon-like, impish form. These are the three powers he uses in the film.)
• Silent Teleportation (Jack-Jack instantly shifts from place to place.)
• Dimensional Travel (Jack-Jack travels between dimensions to appear in a different location.)
• Intangibility
• Optic Blasts
• Wall-crawling
• Psychokinesis
• Size Manipulation
• Electricity Manipulation
• Superhuman Strength and Agility
• Super-humanly Acute senses
• High Intelligence/Omnilingualism
• Density Control (Invulnerability & Intangibility)

Edna Mode did not know what powers Jack-Jack would have, so she covered the basics by designing a fireproof and bulletproof, blanket sleeper like jumpsuit for Jack-Jack.