Promoting a movie is tricky. On the one hand, you want people talking about it ahead of its release, but on the other, you don't want to give away the whole plot. Of course, we're ignoring the fact that most movie trailers these days run for about 20 minutes and proudly feature all of the best scenes from the film, but we're trying to give Hollywood the benefit of the doubt here. Besides, promotional materials have much better ways to spoil their own movies. Like how ...
Movies Are Frequently Spoiled By Their Own Tie-In Toys
You'd think there would be someone in charge of making sure the merchandising doesn't ruin the actual movie, kind of like an inverse Transformers scenario. But it happens surprisingly often. Toy Story 3's Lego set, which hit stores a full month before the movie came out, showed not only the true villain of the movie, but also the pivotal climactic scene wherein he tries to murder the main characters -- and even exactly how they are rescued from it.
LEGONo plot assembly required.
DC debuted an action figure at a toy fair over a month before the theatrical release of Batman v. Superman which showed Lex Luthor in his eventual prison pajamas.
MattelHe's arrested for crimes against acting.
The Captain America: Civil War trailers tried so hard not to spoil the scene in which Ant-Man shifts into Giant-Man. But they really shouldn't have bothered, because this giant-headed screw-up came out months prior: