Ice Cream Guy is one of the Candy People. In "Mystery Train," he is one of the final suspects for the passengers' murders until he becomes a "skeleton" shortly after Finn accuses him of being the murderer. Lollipop Girl supposedly has a crush on Ice Cream Guy because in "Mystery Train," Pineapple Guy plays a song that reminds her of him. During the movie scene of "Go With Me," Ice Cream Guy was seen kissing Lollipop Girl.
In "Mystery Train," Ice Cream Guy is a waffle cone with a single scoop of mint ice cream, but in "Go With Me" his head is wavy strawberry ice cream, and his eyes and mouth are on the cone rather than on his ice cream. It may be that these are two distinct characters, or that Ice Cream Guy is somehow able to change the flavor of his ice cream.
Candy People skeletons
Lollipop Girl and Ice Cream Guy in "Mystery Train."