The Starlight Mansion and its foster webcomics are overseen by Jerrica Benton, the owner of Starlight Music after the death of her father. While she's helped out in her duties by her boyfriend Rio, the chief financial support for supporting the household comes from managing (and secretly performing in) her company's biggest musical act: Jem and the Holograms.
Using a secret high-tech computer built by her father before his death, Jerrica is able to use specialized earrings to project a holographic overlay that turns her from Jerrica into Jem, the most popular singer in the music world. Her band is comprised of her sister Kimber along with her friends Aja Leith and Shana Elmsford. In the middle of the series, a fifth member joins the Holograms, Carmen "Raya" Alonso. Only the other Holograms know of Jerrica's dual identity.
The Holograms' chief antagonists throughout the series are The Misfits (no relation to the real-world band). Formed by Eric Raymond, a former co-owner of Starlight Music, they were chief in his plan to take over Jerrica's part of the company, but were defeated in a Battle of the Bands and had to strike out on their own. The two bands clash numerous times, with the Misfits usually resorting to less-than-legal means, but Jem for some reason never wants to press charges, deciding instead to defeat them in fair singing combat. Or something. The band initially was just Pizzazz, Roxy, and Stormer, but they gained a new British saxophonist, Jetta, at the same time the Holograms expanded to five members.
At the start of the final season, a third band enters the scene. The biggest musical act in Europe, the Stingers come into the neighborhood and start causing trouble for both the Holograms and the Misfits.