Planet 51 was a blast

Just saw the CGI-animated movie Planet 51, very much enjoyed it. Some tidbits:

• Tons of little sci-fi asides, like a shot that echoes the flying bicycle shots of E.T.
• The titular planet is effectively in its own 1950s. No explanation for this is offered. But the styling of all vehicles and buildings and props is Popular Science UFO meets widebody 50s cars. At least one of the vehicles looks like a moving Denny's.
• John Cleese has a fun voice role. So does The Rock.
• The main character, Lem, is voiced by a guy who also did a voice in Terra...another recent scifi animated flick that was good.

SPOILER:

One thing: this one chronicles earth-meets-aliens with a happy ending.But it's about a single earthman visiting the planet, and being surprised to find life there. I don't hold out a lot of hope for a happy sequel. Imagine what happens when earthmen return in force, with McDonalds and Halliburton in tow? All available historical examples suggest total culture destruction.