Here are a couple "fake" Jell-O boxes. Even went as far as putting generic Jell-O in the boxes.
The boxes say 6 Ounce but are 4 ounce size.
I have made several of these for friends with different cards on them. In hand though like Bobs amazing examples they are easy to tell they are not real. One super easy way to tell most fakes is wipe it with a wet cloth. You might clean a little dirt off a real one but the ink from the fakes will be smeared and ruined.