Belldandy and her sisters are based on the Norns, who were the goddesses of fate in Norse mythology. Belldandy (Verthandi) was the goddess of the present. Urd (Urthr, Urdr) controlled the past, and Skuld represented the future. They lived at the base of Yggdrasil, the World Tree. In the original "Aa! Megamisama!" manga, the computer system used by the goddesses is also named Yggdrasil.
Kikuko Inoue actually did most of Belldandy's voice work, actually voicing about a dozen of the 48 shorts in the Mini-Goddess series, as well as Belldandy herself in both the OAV and the TV series.
There are a few witchcraft easter eggs hidden within the anime series. In the anime show, Keiichi Morisato receives a phone call from Belldandy, who then shows up in a mirror and tells him that she visits good souls who are in distress to grant them good fortune. In witchcraft, select people receive "The Call of Hekate", Triple Goddess of the Crossroads. She visits people who are in serious emotional distress to help them make decisions that could better their lives, and never reveals her identity until after the deed is over. When Hekate visits during the night time, if you have dogs, the dogs will be howling for no reason and you'll receive a sort of intuition on how to fix your problems. Mirrors are also said to be gateways to the spirit world during witchcraft candle invocations.