Little Deviants (7/10) is currently free on the PlayStation Store for European PS Vita owners. It was previously £11.99 (or your currency of choice) but unannounced now appears to be free of charge.
There was a demo previously available with an unlock required, but it’s the unlock that’s currently free. It certainly doesn’t look like a mistake.
Developers BigBig were closed by Sony last year, just before the game was released.
Update The price is now showing as £6.99.