Why would the phrase “James is the Santa Claus of gym class” NOT be considered an effective analogy?

Something you may do if the weather's nice on sunday. -something you might not want to do this evening. -something you could go on aaturday evening. -something you could wear to a party. -somebody you might see in the next couple of days. -a subject you could study at college or university. -somewhere you might go on holiday .