Tank (Lilo & Stitch)

Tank, A.K.A. Experiment 586, is an illegal genetic experiment created by Jumba Jookiba. He is designed to eat metal and grow exponentially larger with all that he consumes. He was captured by Gantu, but was rescued in "Snafu". His one true place is at a junkyard eating scrap metal.

Personality
Tank is a gigantic experiment whose intimidating nature only grows with his size. He is shown to be insatiable and voracious, having an enormous appetite for metal. He will hurt anyone who gets in his way and can hold a grudge against them, like he did with Stitch, but otherwise ignores people who run from him.

Lilo & Stitch: The Series
Experiment 586 was the 586th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to consume metal and grow exponentially bigger with each feast. 586 and the other first 624 experiments were deactivated and smuggled to Earth by Jumba during his mission to capture Experiment 626.

All of the experiment pods were released and scattered across the island of Kauai, with 586's pod landing in a car's grille.

When the owner washed down his car with a hose, 586's pod got wet, activating the experiment. 586 then ate the driver's automobile, leaving only the rubber tires, and ran off.

Later, 586 devoured a huge factory that was being shown to some tourists driving in a van, and proceeded to eat metal throughout town until he grew to a large enough size to go on a rampage.

Gantu had been informed about 586 and realized he couldn't possibly catch the experiment in a containment orb, due to how large it had grown. He then prepared the cargo bay of his ship for abducting 586.

Meanwhile, Lilo won tickets to the Elizabethan Fair and invited the hula girls (who ditched Mertle when she refused to participate with Lilo), but neglected Stitch when he told her an experiment was running wild. Later, Stitch (who couldn't attend the fair because no dogs were admitted) teamed up with a lonely Mertle in hopes of stopping 586.

Stitch and Mertle evaded the gigantic 586 in Nani's dune buggy after he got distracted from his metal-eating feast. At one point, a tractor beam abducted Stitch and Mertle into Gantu's ship. Though Gantu was briefly discouraged that he failed to capture 586, he locked Stitch and Mertle in teleport chambers and prepared to try again.

Experiment 625 was inexplicably fascinated by Mertle. She eventually used this to her advantage by soft-soaping Reuben, who released her from confinement as a result. Mertle then locked Reuben in the teleport chamber, and after she freed Stitch from the adjacent one, they escaped the ship as well as 586's clutches.

Gantu later chased down 586 in his ship, but the former was thwarted by Lilo, who brought down Gantu's ship and had two jugglers hinder his progress. Meanwhile, Stitch attempted to battle 586, but the latter proved impossible to defeat, regarding his enormous size and despite Stitch's best efforts.

586's rampage continued to spread, where, after an attack on Stitch, he was abducted by a tractor beam from Gantu's ship. However, Lilo ultimately convinced Gantu to get 586, named Tank, away from Stitch, since the latter appeared to be outmatched.

Shortly after Tank's defeat, Mertle broke off her temporary friendship with Stitch when the hula girls decided to take her back, and Lilo made amends with Stitch.

It can be presumed that Hämsterviel was somehow able to shrink Tank to a smaller size and confine him in a container.

Tank reappeared in "Snafu", and was freed along with Gantu's other captive experiments by Lilo, Stitch, and several other experiments in a rescue mission.

Leroy & Stitch
The first 624 experiments, including Tank, were rounded up by Leroy and taken to a stadium to be destroyed. However, Lilo, Stitch, Jumba, Pleakley, Reuben and Gantu arrived before the experiments could be destroyed.

Tank participated in the following battle between the experiments and the Leroy clones by eating attacking Leroys.

However, the Leroys soon gained the upper hand in the battle, but were defeated when Lilo, Stitch, Reuben and several other experiments performed the song "Aloha `Oe", which caused the Leroy army to shut down due to the original Leroy's fail-safe.

Trivia

 * Tank has shrunk from a massive size back to his normal size between his episode and "Snafu", suggesting that he returns to his normal size after a while without eating any metal.
 * Tank's pod color is blue.
 * Tank is described by the experiment computer screen as, "Experiment 586. Primary function: Metal consumption. The experiment becomes bigger with everything it eats."
 * Tank's ability to grow larger from eating metal is similar to Fudgy's ability to grow larger from eating chocolate in the Stitch! anime.
 * Tank appears in the online game Lilo & Stitch: Alien Interception along with Plasmoid, Dupe, Clyde, Yang and Hämsterviel.