Human Bill Cipher is a humanoid dream demon that curretly roams around Gravity falls his apperance includes a black tophat with yellow robe-like clothes. He has black clothes on his hands and has a cane. Bill also has a bowtie and a triangle shaped eyepatch. Bill's hair is mostly yellow with a black stripe.
Bill likes to make rude insults/jokes. Bill seems to like weirdness as shown in the last three episodes of Gravity Falls. Bill never seems to want to hurt the Pines family, as even in weirdmaggedon he lets his minions do it.
Bill was first summoned by Gideon to enter Stan's mind. Ever since then he has followed the pines twins.