Jack-Jack's History
Jack-Jack is a baby and the youngest child in the Parr family; his parents are Mr. Incredible (Bob Parr) and Elastigirl (Helen Parr). His primary power is shapeshifting, but has a large number of other powers.
For the first year of his life, Jack-Jack didn't seem to exhibit any signs of powers, presumably being too immature for superpowers to manifest. According to official sources, Jack-Jack is 1 year old, is 2'4" (0.71 cm) in height and weighs 30 lbs (13 kg).
Jack-Jack is first seen being bathed by his mother Helen in a kitchen sink while Helen talks with Bob over a telephone, telling him that the family has just moved in. During the scene where the family is having dinner, Jack-Jack is shown to enjoy watching his older siblings Dash and Violet fighting (Dash teases Violet about her crush on her schoolmate, which insults Violet). When a doorbell is rang by a family friend Lucius Best, which also stops the fight and makes the Parrs return to their seats, Jack-Jack turns to the door and asks "Hello?"
When the rest of his family is occupied with a super-villain named Syndrome, Jack-Jack is looked after by Kari McKeen. But her determination to have some fun ends with trouble when Jack-Jack begins showing signs of his powers that she tries to control and eventually anticipates. Later, Syndrome shows up, and Kari, thinking he is the replacement babysitter, eagerly places Jack-Jack into his care.
When the Incredibles return home, they find Syndrome with Jack-Jack in his hands as he openly declares that he will raise him to become his sidekick. With that, Syndrome kidnaps the baby and flies away to his jet, but Jack-Jack uses his powers to defend himself against Syndrome by turning into a fireball, a heavy steel ball, and a small monster. He disables one of Syndrome's rocket boots, causing the supervillain to fly uncontrollably and crash into his jet; upon impact, Syndrome drops the baby. Jack-Jack is rescued by Elastigirl, who is thrown into the air by Mr. Incredible on her command. As Elastigirl turns herself into a parachute to bring Jack-Jack safe to the ground, Jack-Jack notices an explosion way above her (Mr. Incredible has thrown his car at Syndrome's jet, knocking Syndrome off balance, and Syndrome?wearing a cape?gets pulled into the jet's turbine, leading to his death and the destruction of his jet). Soon after Elastigirl and Jack-Jack lands safely on the ground, the wreckage of Syndrome's jet falls onto the Parrs and their residence, destroying their house, but the family survive thanks to Violet wrapping her force-field around them. Jack-Jack also chuckles to Dash's remarks of the possibility of the family having to move again.
Three months later, Jack-Jack is seen with his family at Dash's track race. After the race, The Underminer emerges from underneath the earth and declares war, and the family, including Jack-Jack, put on their masks.
Edna Mode made costumes for the entire family, including a flame-retardant jumper for Jack-Jack which, coincidentally enough, is needed as Jack-Jack has the ability to burst into flames and become bulletproof, though this being done before the family could determine the full extent of Jack-Jack's powers. Edna will presumably modify the costume to accommodate all of Jack-Jack's abilities.
