“A person is a person no matter how small…” No, not a misjudged Disney departure into pro-life propaganda, but the tale of ditzy heffalump Horton (Jim Carrey) who hears a voice squeaking out from a speck of dust and makes contact with the microscopic world of Whoville, home to the Whos and their harried mayor (Steve Carell). Ex-Pixar staffer Jimmy Hayward's adap of Dr. Seuss' 1954 book is seething with a gloopy, candy-gloss texture you’ll want to reach out and poke. But it struggles to rolling-pin the already wafer-thin story out to 90 minutes. Still, the Carrey/Carell voice combo sustains a kinetic comic charm, while Whoville’s wonderfully rendered manic mechanics are faithful to the Seuss source. And talking-animal animations that encourage kids to debate the existential implications of parallel realities are surely a good thing.