The trivia item below may give away important plot points.
Despite Qber's laughing it off, each "grayble" does, in fact, involve one of the five fingers in addition to one of the five flavors. The first scene (Finn and Jake) involves thumbs and includes a sweet plum. The second (Marceline) involves the index finger and savory licks The third (Tree Trunks) involves the middle finger and a sour taste in her mouth. The fourth (Ice King) involves the ring finger and salty tears. And the fifth scene (BMO) involves the pinky and bitter tea.