After looking over Shifter for a build, I noticed that they use the same class feature (Wild Shape) as a Druid. Wild Shape depends on Beast Shape (among other similar spells), which is a spell of the Polymorph subschool. After looking to see what polymorph spells do (link), nothing says that you change your creature type, so even if your body is physically a bear, according to magic you're still a humanoid.
Enlarge Person can target any humanoid. Since a Druid or Shifter in Wild Shape still counts as a humanoid (according to magic), can a Wizard/Sorcerer cast Enlarge Person on the large bear, make them a huge bear, and grant the benefits of Enlarge Person? I can think of a few ways for Wizards and Sorcerers to potentially cast Enlarge Person after Beast Shape (or another polymorph spell) on themselves, but this seems like the most common potential scenario.