Other Mother's minion
Other Wybie is the alternate version of Wybie Lovat.
It is mentioned that Other Wybie "told" the Cat about the Other Mother's intentions, the Cat passing it along to Coraline.
Other Wybie was forced to smile by Other Mother despite it being against his will. Throughout the story, Other Wybie helps Coraline escape a dark room as The Other Mother has trapped Coraline in, and forces her to go back to the real world. As The Other Mother finds out Other Wybie has helped Coraline escape, she kills him and leaves his remaining clothing hanged up on a pole on top of the Other Mr. Bobinsky's rooftop, which leads to the end of Other Wybie's appearance.
Other Wybie resembles the original Wybie almost exactly, the sole exceptions being that he looks slightly cleaner, has slightly better posture and that he possesses matching black-buttons instead of eyes.
As opposed to Wybie's flustered and analytical behavior, Other Wybie is much more observant and aware of those around him. He, like the Other Father, is shown to possess a limited amount of free-will, feeling genuine guilt when helping the Other Mother's plans, also contains a lot of soul sand and helping her escape when Coraline became aware of her evil intentions.
He has been incapable of speaking due to the Other Mother, as she knew that Coraline would find Other Wybie much less of an annoyance to her. It's unknown whether or not the Other Wybie's mouth was made shut or if The Other Mother hurt him enough to keep him quiet, the Other Mother simply saying that she "Fixed him". The other mother had to hurt him in order to keep him quiet.