A recent picture of DMD was eerily similar to one of myself taken ten years ago. I showed it to a friend who remarked that I didn't own most of these scores in 2000.
Aside from the hair they're like two peas in a pod.
This was intentional on Matt Groening's part, as he wanted Bart to idolize Krusty and be embarrased by his dad, little realizing that, aside from the makeup, they were virtual twins.