Double Dee wears a black hat (what's under it, nobody knows), redish orange shirt, and purple shorts. He is a scientific genius, and an obediant little teacher's pet. He enjoys learning and researching.
He also enjoys entomology, the study of insects.
Double Dee is forced to help Eddy with his "scams", so that they will succeed. Double Dee is the only reason that some of them come close to succeeding. Without him, Eddy's ideas would be just that: ideas. Double Dee invents things that help out.
He is the only one of the three Eds that doesn't have a sibling.
He has multiple *freaky* shrine sites dedicated to him, including a part of the Ed Zone.
Double Dee, that's so cute!
~That episode with the middle name theme.