The Painting of Akira From The Simpsons

This is Akira, a voice in the series voiced originally by George Takei and later on Hank Azaria. He was a karate instructor and once told Bart that to be able to break bricks with his head, he needed to first fill his mind with wisdom.
The typical Bart went on to skip the tutorial and bumped into Homer at the mall where they both discovered Flanders' leftorium.

Its been years since I last saw this so forgive me if I mix up a detail or two.