Shadow is a ghost that belongs to Johnny 13. It lacks a distinct identity or personality beyond its joy for creating havoc, as it is always seen smiling when it attacks. Johnny can summon him by whistling.
Shadow first appears in the episode "13", serving its owner Johnny 13. It forces the Fentons' Ghost Portal open to allow Johnny and Kitty through, and continues to serve Johnny as he tries to woo Jazz. It is implied by Kitty that Johnny's "unlucky" reputation is due at least in part to Shadow's actions, as "bad luck" occurs whenever it interacts with the environment, even when it doesn't actively influence anything: Things are seen to fall apart or malfunction when Shadow simply goes through them, which makes it appear as though said things have acted up on their own accord, which caused Tucker to be considered bad luck when Shadow repeatedly meddled with things whenever he was around.
Shadow appears again in the episode The Ultimate Enemy," pushing a wheelchair-ridden Johnny around. While Johnny appears to have aged, Shadow hasn't changed at all, suggesting that, while bound to serve him, it and Johnny are essentially two separate ghosts.
Shadow also has some of the properties of an actual shadow, temporarily vaporizing when bright light hits it and not mixing well with water. It can also hide within Johnny 13's "natural" shadow, merging into it and becoming indistinguishable from it until it is called on, as it was not seen at all under the motorcycle until it was required to hold the portal open for them. During a few situations in which Johnny sends out Shadow, Johnny is seen without a shadow of his own briefly. However, there are also times in which Johnny is seen with a shadow even after Shadow is sent out, so this may just be an oversight.
Powers and Abilities
Shadow's powers all center around bad luck. When he passes through an object, it breaks.
In bright light, Shadow dissipates. In contact with water, Shadow becomes a puddle of black goo. Both of these conditions render Shadow powerless.
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