According to the Legal Post, the most-read Canadian court decision of 2012 is Langevin, 2012 QCCS 613 (CanLII). A claimant calling himself Sylvio Langevin (who has filed various claims under other names) claimed ownership of the planet Earth, as well as, in a separate application, the planets Mercury, Venus, Jupiter, Saturn and Uranus, in addition to the four largest moons of Jupiter.
Mr Langevin apparently “saw a unique opportunity in the planets“, and reportedly “thought he could start a collection, like other people collect hockey cards“. Since the five planets and four moons are “errant” the claimant was certain that the planets currently had no legal owner.
You can consult the judgment (in French) here.