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[edit] Different credits

You can see different credits than the ones when you photograph Mew. All you have to do is finish your Pokémon Report, then Professor Oak will congratulate you. Different credits that you'll only see once will roll in.

[edit] Cave Stage

Cruise near to the end and you will find a brown wall and a switch to your right when you close in on the exit. Look closely, and you will see a Porygon resting in a chameleon form in the wall. Hit it with a Pester ball and the Cave is unlocked.