Pendleton also plays the ukelele on it. Some of the music used in the series is recorded inside a pirate ship that the show's composer built inside his flat!
Finn the Human was voiced by Zack Shada for the first few years but as he got older his voice changed so his younger brother Jeremy Shada (pictured) replaced him
The series is due to finish in 2018 but it's not all bad news. Firstly, there will be close to 300 episodes by then, and secondly, they're going to wind the whole thing up with an Adventure Time movie!
They have 3 daughters - Charlie, Jake Junior and Viola - and 2 sons, TV and Kim Kil Whan. He's also a very talented skateboarder.
This means she can play her bass (which is made from her ancient family battle-axe) either way around
They even met in an episode of Adventure Time!
Can you spot him?