So how about a real joke about Bulgarians for a change?

A flying saucer beams up a German engineer, an Indian guru and a Bulgarian. The three of them are informed by an alien in a lab coat that standard procedure when contacting an unfamiliar species is to subject them to the standardized intergalactic intelligence test.

"You will be put in an airtight vault for three minutes," says the alien. "It's 3x3x3 meters and completely empty. You'll be given two balls made of a superstrong titanium alloy and no tools. Do something in the vault that will convince us that you're more interesting to us alive than dead, because if you fail to demonstrate your intelligence, we'll dissect you."

First goes the German engineer. After five minutes, the scientist alien walks into the cockpit with a disappointed look on his face.

"So we open the vault and he has managed to balance one ball on top of the other," reports the alien to the captain. "I ask him how, exactly, is this supposed to convince us that humans are an advanced species. Apparently "knowledge of basic physics" and "manual dexterity" are good enough for a human. Meh. We're dissecting him as we speak, bring in the next one."

They put the guru in, five minutes pass and the scientist alien walks into the cockpit even more disappointed.

"So we open the vault and he's sitting there in a lotus position, the two balls floating in the air around him. He even gives me the "Are you impressed?"-look, can you believe that? Apparently, lifting heavy titanium balls is impressive for the human mind. So yeah, they struggle with basic levitation; we're dissecting this one as well. Send in the last one."

The Bulgarian is put in the vault, the vault is sealed. Five minutes pass and the scientist alien bursts into the cockpit, flailing his arms and shouting excitedly at the captain and crew.

"Guys, you need to see this! Come, leave the saucer on autopilot and come! I swear, I have not seen such a thing in my entire career!"

"Calm down, what has he done?" asks the captain.

"It's unbelievable," continues the scientist, "in three minutes inside the vault he has managed to lose one of the balls and break the other."