They are voiced by Tracy Martin (Bess Grumper) and Courtney Peldon (Courtney Grumper).
They almost got the W.I.T.C.H. gang to break up in the ninth issue, but in the end, they got what they deserved. Cornelia told them there was a "Costume Party" after the Christmas Play, but really, no one else was in costume and the two conniving sisters were, much to their embarrassment and everyone's surprise and tremendous laughter, hilariously sitting around in pink-and-purple, puffy, ballroom gowns.
In the animated series, episode: 'L is for Loser' they start to work in the school's radio station. After running out of gossip, they decided to 'create some'. They made Martin sing a 'lovey-dovey' song for Irma. Enraged, Irma lashed out at Martin and called him a loser, realizing too late that they were on air (as planned by the Grumpers and Uriah).
Bess and Courtney have also been known to diss Cornelia about her fashion sense, such as in The Stone of Threbe, where they are walking through an alley and dissing Cornelia, causing her to throw a couple mud balls at them which scares them into running away. However, they continue to be gossips as shown in L is for Loser.
The scandalous sisters and the writers of the gossip section of the Sheffield Institute's newspaper. They love to ridicule (especially when it comes to gossiping about others) anyone and get them in trouble at school to see their reactions, but the W.I.T.C.H. girls - and especially Irma and Cornelia - are their favorite targets. They are considered to be Principal Knickerbocker's pets, though they don't mind bribing students to stand behind them. They are considered rude by everyone except themselves due to their gossip nature.