The characters are caught at a wall, the enemy is too smart/strong/numerous or any number of things that prevents them from continuing forward. The problem is only solvable when they stop thinking along their normal mindset and start thinking outside the box.
Note that this isn't doing something crazy or unexpected and it works because it is crazy or unexpected, see Crazy Awesome
for characters that do that on a regular basis. This is specifically about breaking away what is considered the proper way to do things and finding an unexpected solution.
- In Buffy the Vampire Slayer, the Grand Finale has Buffy contemplating the fact that the enemy has an actual army at their disposal and she is a lone slayer. Realizing she is a lone slayer, she starts to question why it has to be like that and thus decides to eliminate The Chosen One rule and make all potential Slayers full Slayers.
- In Attack of the Clones, Obi-Wan is perplexed over tracing an item to a planet that his friend recognized but was not in the Jedi archives, which is a supposedly fully comprehensive database. Asking Yoda about it the question is brought before a group of Jedi children, with one suggesting the information was deleted from the Jedi records. Since only a Jedi could have had access to the archives the possibility of internal tampering did not occur to the older Jedi.