In this episode Amy does indeed wear pierced earrings. You can clearly see the entire lobe surrounding the blue earrings when she gets her photo taken at the prom. However, in season 9 episode The Bachelor Party Corrosion (2015), Amy claims to have never had her ears pierced.
Sheldon points out that kings aren't elected, but for a period of time in Poland, many kings were elected by the Sejm, and, similar to the Pope, serve for life, and upon their death or abdication, a new one is elected.
Sheldon says that the classification of 'lesser apes' was created to single out the gibbon as different from the greater apes. This is misleading since 'lesser ape' encompasses 16 species. The classification of 'greater apes', however, only includes 7 species.