Lumpy is a young heffalump whose full name is "Heffridge Trumpler Brompet Heffalump, IV." Since his name is so very long, he is almost exclusively referred to as "Lumpy."
Lumpy was introduced in the film Pooh's Heffalump Movie, When Roo joined the heffalump-hunting expedition without his mom’s knowledge, he ended up discovering Lumpy and captured him. Roo soon discovered that none of the scary things Rabbit and the others had told him about heffalumps were true. The two became fast friends and were seen celebrating their friendship in the song "Shoulder to Shoulder," in which Lumpy finally "uncaptured" himself.
Lumpy returned in Pooh's Heffalump Halloween Movie. He became a semi-regular character in My Friends Tigger & Pooh, voiced by Oliver Dillon. Lumpy has a stuffed alligator named Alvin. He is fond of the snack rumpadoodles.
Lumpy does not appear in the 2011 film Winnie the Pooh, which is explainable due to the fact that the film was based on five original stories by A.A. Milne, and therefore Lumpy had not been created yet.