The Queen went behind the bar at the Queen Vic pub
At the Blue Peter studios at BBC TV Centre, the Queen met a line-up of the long-running show's hosts, including Valerie Singleton, Peter Purves, Peter Duncan and John Leslie.
She was then presented with a gold Blue Peter badge, saying: "How splendid."
Current presenter Simon Thomas joked that it might help her get into some attractions for free, including the Tower of London.
"She laughed, which was good because I thought, if the joke goes wrong, I'll look very silly," Thomas said afterwards.
Earlier, EastEnders actresses Wendy Richard and Barbara Windsor showed the Queen and the Duke of Edinburgh around the EastEnders set in Elstree.
The Queen was shown around by Windsor, who took her behind the bar at the Queen Vic pub, named after her great-great-grandmother, while Prince Philip was given a tour by Richard.
"She was marvellous - she made it very easy because she asked us all the questions," Windsor said.
"I think maybe if she wasn't a fan, I think she is now. It was fab."
Windsor also dismissed reports of a row with Richard over who would escort the royal party as "a load of old nonsense".
'Very interesting'
After watching a rehearsal, the Queen was asked if she would like to go behind the Queen Vic bar and replied: "I would love to."
"She said it was very interesting and remarked on how tiny and narrow it is," said Windsor. "I think she was amazed at how small it is."
Steve McFadden, who plays Phil Mitchell, asked both the Queen and Prince Philip whether they watched the show - but they said they rarely had time.
"I have seen part of one episode, but it always comes on at the worst possible times," Prince Philip told McFadden.
Prince Philip was also given a demonstration of special effects by Adam Woodyatt, who plays Ian Beale.
The Queen and the Duke of Edinburgh also toured ITN's news headquarters in central London, where she was given a personal update from the Afghan front line by videophone.
News anchor Sir Trevor McDonald escorted her around the studios, from where she was introduced to reporter Tim Ewart via a video link.
The Queen was also shown the broadcaster's hi-tech virtual reality studio, where presenters can stroll around computer-generated backgrounds, by Dermot
Murnaghan.
Meanwhile, Prince Philip was shown around by newsreaders Katie Derham and Mary Nightingale.
The royal couple dropped in unannounced on the ITN 24-hour news channel - but presenter Rachel McTavish managed to maintain her composure despite their presence behind the cameras.
The Duke was also due to visit BBC World Service, particularly the Persian and Pashto sections, and Classic FM's radio studios.
The day will finish with a reception at Buckingham Palace for people working in the broadcasting industry, including back-room production staff, presenters and reporters.