Cloudy typically appears as a sentient pink cloud with eyes (usually blue, sometimes green) and a mouth. When summoned while Star is channeling her magic negatively, Cloudy appears green instead of pink.
From "Club Snubbed" onwards, Cloudy's appearance is different. He is now a darker pink, with wings on his sides.
In "Wand to Wand", Cloudy appears green instead of his usual pink when Star channels negative emotions while casting Summoning Cloudy Charm. While in this state, Cloudy is sluggish and carefree, creating a big mess around the Diaz Household and not caring. When Star tries to zap him back to normal, he gets mad and grows into a furious storm cloud, impervious to many of Star's magic spells. It is only when Star channels her positive emotions again that her magic finally turns him back to normal.
In "Club Snubbed", Star conjures up Cloudy to help her confront Tom. In "Stranger Danger", Star uses him as part of her plan to regain her wand. In "Starfari", Cloudy appears as Star helps the monsters save their village. In "Ponymonium", Star flies on Cloudy to and from the Cloud Kingdom of the Pony Heads.
On most occasions, Cloudy appears bright and smiling, happy to help Star in any way he can. When influenced by Star's negative magic, however, Cloudy is lethargic, carefree, and somewhat passive-aggressive. He cares little about the consequences of his actions or about Star's wishes.
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