Fluffy is Perfect Peter's female white Persian cat who feuds with Horrid Henry's hamster, Fang. In one episode, Fluffy is a male. Fluffy appears in most episodes sitting by the sitting room window still at night, and as she clicks the TV remote control button next to her, the scene changes to sunrise. In Series 4, she uses the tablet.
Fluffy is incredibly lazy and like other cats normally eat, drink, walk, and sleep. In the books, she mostly sleeps, making her nearly the opposite of Fang. She loves scratching up the sofa and mostly shedding up some paper with her claws as shown in Horrid Henry, Nothing But The Truth twice (first was in Peter's story when she shreds up Henry's homework and the second was in the end when she shreds up Peter's true story of Henry he's making) and the ending for Horrid Henry's Diary. She also appears to be addicted to tickly treats. In Horrid Henry and the Catastrophic Cushion, she loves sleeping on the sofa and the Gross Class Cushion. She is an amazing dancer when it comes to music.
When Henry goes downstairs, he mostly steps on Fluffy's tail, but in Horrid Henry Where's Fluffy?, Fluffy cannot stand Henry tormenting Peter, so she runs away. She appears to provide a great distraction for Henry in Horrid Henry and the Best Boy's Club Sleepover. However, she furiously shreds Henry's diary after Henry insults her in Horrid Henry's Diary. In later episodes, she likes Henry a lot as they watch TV.
Fluffy loves Peter very much, and in Horrid Henry and the Tickly Treats Thief, she makes herself very innocent when she was accused of stealing the gummies. This made Peter cry because he was defending Fluffy.
Fang and Fluffy have a stronger friendship in Series 4, they use the tablet to play music and then dance together, they also take pictures with it, this is first shown in Horrid Henry Takes the Blame. Fang and Fluffy also team up in Horrid Henry's Animal Antics.
Fuffy appears to be a small, bluish-grey cat with green eyes and a blue collar with a yellow name tag.
- Fluffy normally uses the remote during the night to switch to sunrise, but at the arrival of Series 4, she uses the tablet.
- She is lazier in the books, but she can dance in the TV series.
- In Horrid Henry Where's Fluffy?, even though Fluffy isn't there, the sun still comes up.
- In Horrid Henry Where's Fluffy?, Fluffy is a referred to as a male but in the rest of the series, she's referred to as a female.