Even though the original concept wasn't his it's interesting to go back and see how much stuff Satoshi Kon put in that he'd later use again.
Mixing of reality and fantasy - basically everything he's done
Film within a film - basically everything he's done
The internet - Paprika
Skipping girl - Paprika
Fractured storytelling - Millenium Actress, Paprika
Creepy nerd - Paranoia Agent
and I'm sure there's more