One California family built the ultimate father-son project: A roller coaster.
Lyle Pemble, 10, wanted to build a real roller coaster after visiting an amusement park, according to ABC News.
Dad Will Pemble, 50, actually gave it the go-ahead, as he knew his son was a type of roller coaster savant.
"He's a studier. My son knows everything there is to know about roller coasters. He helps design them and does the math," he said.
Cut to six weeks later, and "The Caution Zone" was complete. The 200-foot backyard roller coaster meets rigorous safety precautions and travels 14 mph -- powered solely by gravity.
And get this: Lyle and his dad have begun building another roller coaster for a friend!