I have to question the decision to dedicate this animated adventure about a couple of young wolves (voiced by Justin Long and Hayden Panettiere) from opposite sides of the pack to the late Dennis Hopper. I can fully appreciate the desire to honor his last performance, but everything about his work here — and the movie as a whole, if truth be told — just feels wrong. Grade: D.  

Nanette Burstein, whose “documentary” American Teen proved a nice warm-up for the romantic-comedy hijinks here, works from a script by Geoff LaTulippe that tries hard to inject new life into a long-listless genre. The surprise is that it often succeeds, delivering unique character details (its use of pop culture is relatively keen) and a central duo that seems naturally at ease. Grade: B-.  

Many of the comparisons that will be made about this animated tale will focus primarily on the space-age science-fiction variety because it's packed to the gills with references to everything from 'The Day the Earth Stood Still' to 'Wall-E' and 'Star Wars.' But at its rather sweet core, 'Planet 51,' despite all of the who's-an-alien jokes being bandied about, the most appropriate and loving homage in the movie is toward the 'Back to the Future' series. Grade: C plus.