At its peak, the series had 15 million viewers. The production team opened almost 5,000 letters a day, 20,000 letters a week and upwards of 250,000 letters a year. Jimmy Savile joked that people who misbehaved at the BBC were made to sort the letters as punishment. Roger Ordish said that the production didn't reply to every letter, because the postage would have cost more than the show's entire budget.
There were more than 1,500 'Fix Its' over the course of the series.
He "magic chair" was invented by Tony Novissimo and was built for the BBC by him at his workshops in Shepherd's Bush. The chair had first appeared on Jimmy Savile's earlier Saturday night TV series, Clunk-Click (1973). The chair was later replaced by a new computer-controlled robotic "magic chair", the brainchild of Kevin Warwick, built for the BBC by his team at the University of Reading. The arm for the chair was an RTX robotic arm, designed by Roy Levell at Universal Machine Intelligence in Wandsworth around 1985.
Some children apparently thought that Jimmy Savile's first name was "Jim'll", so some letters shown on the programme started "Dear Jim'll".
Internally, the BBC were concerned that the show was providing excessive product placement for corporations.