Ghost Ian is one of the ghosts that appear in Epic Mickey and in its sequel. Like Gremlin Prescott, in the first game Ian appears as a minor character, but in the second game he plays a much bigger role.
In Epic Mickey
In the first game, Ian was one of the many ghosts that had to move out from Lonesome Manor to Bog Easy when the Pipe Organ went crazy. Before Ian and all the other ghosts moved out from their home, one of Madame Leona's books flied out of her library to Bog Easy and she blamed Ian for it. So the player has to recover the book for Ian and return it to Leona.
In the sequel, Ian acts as the "self-appointed caretaker of Blot Alley and the Spatters" (described by Gremlin Gus). You first meet him when entering Blot Alley, then he explains that he dosen't see a lot of Toons because of their fear to get chewed on followed by his slow progress in making the Spatters friendly.
Ian can either help the player or difficult him the progress through the game depending on how you treat the Blotlings in Blot Alley and Fort Wasteland. If you befriend the Spatters in Blot Alley, he'll open the gate to Club 13 for you and give you the Spatter Whisperer Pin. If you thinned some of the Spatters, he'll still open the gate and he will give you some E-Tickets for all their troubles after a not-so-good of a run. Either way, Petetronic would tell you that Ian will give you the Floatyard's entrance ("If you don't mess with the Spatters, that is!") If you thinned all the Spatters, Ian will still open the gate but this time will give you nothing and leave Blot Alley ("If we cross paths again, ya better hope I'm in a better mood!"). Petetronic will then tell you to find the entrance on your own since Ian is not in your holiday list anymore.
In Fort Wasteland, if you befriend the Spatters and Deloris the Slobber, he'll open the projector screen to the Floatyard and give you a Flower costume. If the Blotlings are thinned, he won't open the projector screen, but the archaeologists will open you the D.E.C to the Floatyard; also Ian will summon five more Spatters and give the flower costume but in some bad shape that you will have to pay the haberdasher 150 E-Tickets to repair it.
If you choose the bad path, Ian (similar to Small Pete in the first game), along with Deloris the Slobber, could technically be Mini-Bosses of Fort Wasteland.
In the good Ending he will be giving Ice Cream cones to a pair of Spatters, while Deloris will be offering an Ice Cream cone to Paulie. In the Bad Ending, the Spatters will be throwing Ice Cream at toons (including a dog, Rufus McBark) and Ian.