When the aliens came, they really said "We come in peace". It makes sense really, it's a necessary greeting from the unknown. They came here, first contact was a note saying they needed a clear tarmac and that they were here to trade, and they'd leave us alone if we wanted. It came by radio, in English because they chose to land in Chicago and they did their homework.
They gave us some nifty scientific marvels, extensive star charts and a guide to the planets and life and civilizations in our neck of the Galaxy. That was their best barter- All the knowledge of their 700 years of space travel in exchange for, of all things, cheese.
The aliens were fat. Mega-fat. Fat was their status symbol. If you were fat on their world it meant you had made it in life. If you died of obesity you attained an honor that doesn't really translate to human. And if you were rich enough to be traveling to Earth to trade for new exotic foods to ship home, you had it really good so you were massive. The aliens were almost spherical, and when some of our less-than-dignitaries nicknamed their species that Fat-wads, they were overjoyed to learn the meaning. Truly flattered.
They gave us all we wanted for cheese. They bought up meats and veggies too, but cheese was the big earner for them. They bought it by the ton, literally as they needed 5 tons per flight to make it worthwhile. Mozzarella, Gouda, Cheddar, Swiss. The simple cheeses mostly, but every kind got sales. Their species had nothing like it. Chocolate had a niche market but it was sort of spicy to them, if that makes any sense. It hurt them a little to eat but it was still nice and fatty. They didn't like butter, they had something like it back home and considered it dull. But the cheese industry grew as fat as the Fat-wads from Skort, a teal and white Mars sized planet orbiting the star Ross 154.
Everyone got into the cheese industry, of course. Little companies started to make new, alien oriented cheeses. Big companies in oil and cars got into cheese making. Cows and goats became big business and a big problem. Abuse was rampant, land for grazing was a problem. But we made do, trade is good for nations and better for planets. We even got some tourism back and forth, apparently Earth has a bigger variety of environments, flora, fauna and art than most planets.
We got used to it all in a couple decades and went back to our wars and politics and all that jazz. The aliens had their own problems back home too, politics and colonial issues. They still trickle in from time to time but not like they used to. Some even get stuck here, others like to stay. A couple of 'em landed their space-bound motor home in Iowa and had a kid. He went to school, got his degree, and went to work at the Factory.
So that's what Efengi is, if you were wondering. A Fat-wad from the planet Skort.