The Life-Size Dinosaur is a scam idea that the Eds came up with in "An Ed Too Many". After escaping from Sarah, who had developed a crush on Edd at the time, they set up shop in Edd's garage so they could create this scam. However, soon after starting work on it, Sarah found her way into the garage and managed to wreck the scam along with all the progress the Eds had made on it. She also managed to cover Edd in the quick-drying papier-mâché that they were planning to use to make the dinosaur, ensuring that Edd couldn't move and they couldn't make the scam.
Despite the scam never being completed, it is unknown what its purpose would have been had it been finished. It is possible that they would have charged the kids to see it. It is also possible that they might have let the kids play on it for a fee. However, Eddy might not have come up with a plan to profit from it, instead trusting that something would occur to him once the thing was complete.