Bess and Courtney Grumper are two twin girls known as "The Grumper Sisters". They have bright red hair and glowing green eyes. They love spreading gossip. They are big into fashions and rivals of Cornelia. In season one they join the school newspaper to write about fashion. In the second season they do the gossip on the K-Ship Student Radio and are disliked by many students and especially by Irma because of the nasty rumors they make up about people. They seem to be more or less popular among boys. They have more action in the comics.
The scandalous sisters and the writers of the gossip section of the Sheffield Institute's newspaper. They love to ridicule anyone and get them in trouble at school to see their reactions, but the W.I.T.C.H. girls - and especially 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 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 and puffy ballroom gowns.
In the animated series, episode  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, where they are walking through an alley and dissing Cornelia, causing her to throw a couple mud balls at them.
Season 1 Episodes
- "The Stone of Threbe"
- "Stop the Presses"
- "The Mudslugs"
Season 2 Episodes
- "L is for Losers"
- "O is for Obeidence"
- "S is for Self"