This can be done on the map Goat City Bay. You have to knock down the mechanical bull in the amusement park and a person will jump on your back. You should be able to knock the bull over by left clicking on your mouse or by holding left shift to charge. After you have your rider, head back to the spawn point and up the hill. Get on the catapult and the cheevo should pop once you land. Below is a video, credit to GlassGhost428.