Couldn't Have Done It Without You Trophy

The credits happen after beating the game on any difficulty. Grab some popcorn or a Snickers or whatever as they're pretty long, like 20 minutes long and you have to watch them entirely.

Pro tip: you don't have to watch them, you can let them play and do something else, no one will verify if you're in front of your TV! More seriously though, if you missed this trophy (I didn't see a skip option but it's possible to turn off the console or whatever), the credits can be found in Settings => Account & Network => at the bottom.