For future reference; "Beemo has been confirmed to be genderless. Beemo is referred to as "M'lady" by Finn in "Conquest of Cuteness", but Adam Muto has stated this doesn't mean anything. When being referred to by Finn, he will use masculine pronouns. When referred to by Princess Bubblegum, she will use feminine pronouns." However, since being voiced by Niki Yang, i think of Beemo as a girl.