Perry Bible Fellowship

My interpretation is that the ketchup head sees the superficial similarity of a splatter of red liquid and says he can do that, but he doesn't actually have the inherent qualities that give the bullet's splatter its emotional and artistic meaning.

No matter what, a splatter of ketchup can never carry the same meaning as a splatter of blood and other bodily fluids, so the ketchup head's ability to make something visually similar does not translate into him being able to make something artistically similar.

There's a couple layers to it.

From the artists perspective: people often dramatically underestimate the amount of labor that goes into a piece. It isn't always about skill, sometimes it's about drive. Yeah, ketchuphead could've made it, but they didn't, bullethead did.

From the critic's perspective: Modern art often looks like literal trash, or like someone haphazardly slapped paint onto a canvas and called it art. Ketchuphead believes since this is just a splatter of red they could easily make the same thing.

I think its just funny because ketchup stain

I interpret it as bullethead being a highly-skilled artisan that used ketchup (or similar substance) to create art. Ketchuphead thinks he can recreate the art but is missing the skill to do so and just has the raw materials.