So I'm confused by what exactly we're supposed to send in for this puzzle. Even before getting any clues, the instructions are "Fill the empty space with the related title. . . ." and it is clear that this instruction is to be done twice. There are three ways to interpret this. The second time the instruction is performed. . .
1. there is no longer empty space, so you don't do anything
2. you fill the squares with the new letters, erasing the first.
3. you fill the squares with the new letters, leaving the first letters there, too.
I truly have no idea which of these are expected in the entry.