Most of the music for Wizard101 is composed by Nelson Everhart. You can find his YouTube channel by typing his name and Wizard101 into the YouTube search box!
The humour...everywhere! EG the appearance of enemies, funny fish designs, laugh-out-loud monstrology descriptions, spell animations etc
The distinctive music of each world/instance that immediately makes me feel the way the world makes me feel while exploring and questing there
That there are activities for my wizards no matter what frame of mind I am in irl - fun challenges and story with questing, calming fishing, creative decorating, quick challenges like one-shots, a wide range of badges to collect, pet making and sharing, gardening for when I need to feel more grounded in something predictable and rewarding...etc
I love paying very close attention to the dialogue and the characters. I love when there is depth put behind a character and I especially love when we return to an old character! In Empyrea pt 2 I nearly hit the floor when the Lady of the Lake spoke, and the voice actor was the same from 2012!!! Or else the one who voice her sounded extremely similar.