Sort of funny, but mostly only if you've watched the films it takes off. Even then, the parody element isn't that strong. Rather, they're more like "cameo jokes" in which the gag is getting the movie reference. That said, some gags like those relating to harry Potter and Wonka's factory, are spot on.
Another problem with the film is the ending. Ideally, as the main characters exit Gnarnia back to the interior of Willy's factory, it would have been funnier if we'd encountered Willy once gain, with some gag related to Gnarnia. But, it was not to be.
Yes, I laughed, but a repeat viewing would probably be very flat.