The Lumpy Space Prince is the gender-swapped version of Lumpy Space Princess. He appeared in the season three episode "Fionna and Cake" and the season five episode "Bad Little Boy." In "Fionna and Cake," he was only shown drinking from a blue cup. His second appearance was in "Bad Little Boy," where he was hosting a party.
Lumpy Space Prince appears identical to Lumpy Space Princess, except with a mustache and a darker shade of purple. Like Lumpy Space Princess, he does not have a crown, but the star on his forehead probably indicates his position of royalty.
- Not counting a technicality with Neptr, the only princes shown in the series are Lumpy Space Prince, Prince Gumball, Muscle Prince, Prince Huge, the Box Prince, and Flame Prince.
- Lumpy Space Prince's voice is almost identical to Lumpy Space Princess', as both of them are voiced by Pendleton Ward.
- In "The Prince Who Wanted Everything", he became voiced by Peter Serafinowciz due to Lumpy Space Princess preventing Ice King from using her voice for him; this voice had a British accent rather than a Valley Girl accent.