The idiom "all over the show" means that whatever is being referred to is scattered around everywhere, and is in general disarray. The phrase is related to many other idioms commonly used in British and American English, such as "all over the shop" and "all over the ballpark," which have the same meaning. The phrase comes from the even older saying, "all over the place," dating back to the 19th century.
Idioms are short phrases which cannot be defined by deconstructing their literal meaning. A common idiom used in the English language is to "get your ducks in a row." Someone who utters this phrase should not be thought to be discussing how he or she is in the process of lining up actual birds. The actual meaning of the phrase is someone is paying attention to the details and accounting for all elements before starting a new project. Other idioms include to "beat a dead horse" and to "add fuel to the fire."
Something can be said to be "all over the show" if it is scattered thoughtlessly around any place. This could be used to refer to anything, from toys around a room to punctuation marks around an essay. A person could say "look at this — there are toys all over the show" if he or she was confronted with a room scattered with a child's toys. Likewise, he or she could say "the punctuation on this assignment doesn't make sense; there are commas all over the show" and still be using the idiom correctly.
Fairly unusually for an idiom, there are many different variations on this phrase which all carry the same meaning. Someone is just as likely to say "all over the place" as he or she is to say "all over the show" because the meaning is exactly the same. The original version, "all over the place," is thought to date back to the 19th century, but a definitive history of the idiom is hard to pin down.