Why is Yin so interested in bad boys and is also able to become evil twice? Yin is the sign of darkness of the Yin and Yang symbol (in other words, the black half) so it makes sense why she's naturally like this.
Why is Yang's sword made of bamboo? Master Yo probably made it and pandas do tend to eat bamboo so...
Bonus points in which Master Yo was shown to chew on Yang's sword occasionally.
The writers were fairly accurate in incorporating the aspects of Taoism into Yin and Yang's personalities; also, Yin and Yang's ear shape are much like the Taoism when put together.
In "Disap-Eared", Yang becomes invisible but he messes up the spell to the point that nobody can see, hear, or even touch him; in addition, he's also able to walk through almost anything. It may not seem that creepy at first until you consider that Yang could have been intangible forever which isn't the most lighthearted of fates.