Getting "crossed lines" when you tried to make a phone call. As a child, it was always a source of huge excitement to me, eavesdropping on somebody's conversation. I always hoped to hear something salacious, but the topics discussed were usually banal. But all was not lost: if the conversation bored me, I used to make occasional small noises, squeaks and snorts, until the conversants noticed. There would be a slight pause, they would question each other suspiciously on the source of these mysterious noises, and then one of them would announce indignantly that she thought there was somebody on the line, and they would terminate the call. I thought it was hilarious - my life must have been dull!
Playing on building sites and in derelict houses.
People leaving dogs at home all day while they were out at work.
"Bunny" brand incinerators for sanitary waste in the ladies' loos, along with waxed paper disposal bags featuring a coy-looking Edwardian lady.
Turning on the TV to find nothing on but the Test Card Girl.
In the mid 1990s, clicking onto a website to find the "site under construction" message, along with sort of "men at work" triangle.
Does anyone remember the Cambridge coffee pot webcam?