Jill says "Randy you must be excited about starting high school, huh?"
Randy had already taken classes at the high school because he was advanced.
Wilson claims to be growing yams, but he is holding sweet potatoes. Contrary to popular belief, yams and sweet potatoes are NOT the same thing. Sweet potatoes (Ipomoea batatas) are native to the Americas, while yams (genus Dioscorea), native to Asia, Africa, and the Americas, are much larger tubers with an inedible woody skin.
The micro car would run on a motor not an engine. An engine that size can't exist.
During the "Tool Time" segment at the beginning, Tim and Al show the world's smallest working car. When the car is shown in a close-up shot, the string pulling it can be seen.