If you recall, a few days ago I posted about James and Oliver Phelps being on the television show Blue Peter.  According to a TLC reader:

Just seen Blue Peter where they showed a brief clip of Ron, Hermione, and Harry in the Weasley joke shop. It showed Hermione furtively putting a product back, and then Ron following the twins up the stairs with a product asking how much it was, the twins answered 5 galleons, and Ron quite peeved said I’m your brother and they looked at each other and turned to Ron and answered “10 galleons”. The shop was full of kids and products, it was off-the-wall to look at.

The twins built a mat that shot water up from it if you stood on it and got water sprayed at one of them … They weren’t bothered though. They said they played practical jokes mainly on the crew not really on Dan or the lead cast etc

I will post the video as soon as it comes online!