Was never much into Sci-Fi, but I would assume my favorite TV show fell under "fantasy".
Charmed is an American television series that originally aired from October 7, 1998 until May 21, 2006, when its network, The WB, ceased operation. The series was created in 1998 by writer Constance M. Burge and was produced by Aaron Spelling and his Spelling Television company, with the show runner being writer-director Brad Kern.
Charmed initially starred Shannen Dougherty, Alyssa Milano, and Holly Marie Combs as sisters.
When their grandmother dies, the Halliwell sisters Prudence (Shannen), Piper (Holly) and Phoebe (Alyssa) move into her home. Phoebe goes into the attic, and discovers a trunk with a large book called "The Book Of Shadows" inside. She opens it, and discovers that they are from a long line of witches. It's their destiny to become "the Charmed ones", and protect humanity from demons and evil.
Each sister had a specific power. Eldest Prudence could move objects with her mind. Middle sister Piper could temporarily freeze time, and youngest sister Phoebe could see the future.
After two successful seasons, tensions rose between Dougherty and Milano. Apparently, in the middle of the third season, Doughtery said to producers "either she goes, or I go!" thinking that they would write Milano out of the script. Instead, writers killed off Dougherty's "Prudence" character.
The problem with this was the show was based on the "power of three", meaning the bond of the three sisters.
Enter Rose McGowan.
Season four started with Prudence's funeral. However, Piper and Phoebe discover that they have a half sister that they didn't know existed. When they meet youngest half sister Paige, her powers become active, and she takes over for Prudence, moving objects with her mind.
The show lasted for another 5 seasons, and remained a ratings grabber for the WB network.