Back in april I got 14 surprise prize boxes and one of them had the normal thing in it as well as a Hidden Surprise prize box. I do not have proof since I opened it back in may sadly. I don't know if there is anything I can do to get proof as well.
The "Hidden surprise prize box" Came with two additional prize boxes.
Well I can't do much picture wise. Can't you message support or something?
But I don't think the extra boxes really matter since it was a random prize box from the past year.
This seems incredibly dubious.
Promotion info for April 2015 as well as info for April 2014 do not state that boxes can chain (contain more suprirse boxes). OOO has made mistakes regarding these promotion pages before, but they are usually tiny or a minor dev/game misname (see "power scanner" and "bomb bundle.") They try to promptly fix mistakes, and one this major would definitely have warranted a fix. The promotion info specifically states that you can unbox one of the listed boxes. What you're describing violates both aspects of this statement - "one" and "listed." Furthermore, the additional prize pool is not stated to contain a chance for another box.
We'd likely have heard of this happening from a few or many players at the time if it was a thing, but this does not prove or disprove anything.
What could have happened was an extreme lag spike, seeming to show weird things being unboxed, but if your arsenal actually contained an item called a "hidden surprize box," then that is something that would have been listed. Sadly, we cannot verify the item's icon by name, as many boxes simply recolor a standard icon, and files that would be associated with it would likely have internalized names. If your arsenal contained more items than seemed natural, then you should have contacted support at the time.
If this really did occur, you definitely need to message support yourself (we shouldn't contact support for you about your knight's issues). Why it's being brought up out of the blue now, I don't understand, further enforcing the dubiousness of this thread.
In terms of information, this sort of thing matters quite a lot. History and being able to compare it to itself as well as the present, in order to better prepare for the possibilities of the future, is very important.
What I would have done is contacted support first, verified the phenomenon, and then mentioned to us here that we are missing data that should be added to wiki, if only for historical purposes. With proof of the staff interaction, of course.
We need images, and more information in general. For example: What two extra boxes came out?