The characters were originally conceived as two ageing Shakespearean "old luvvie" actors who were doing domestic work (in Kenneth Horne's flat) while waiting for the next acting job. The producer thought the characters were too sad and suggested making them younger "chorus boy" types.
As well as being highly amusing, Julian and Sandy were notable for being two camp homosexual characters in mass entertainment at a time when homosexuality was still illegal in the UK, and for the use of Polari or palare in the sketches. The writers and cast thought the characters worked very well as they were not being held up to ridicule or simply there to be the target of a joke, in fact most of the sketches revolved around Kenneth Horne's presumed ignorance being the target of their jokes.
Kenneth Horne would find these two characters usually by looking in a rather risque magazine (which he would insist he bought for innocent reasons). This would lead him, more often than not, to a business in Chelsea starting with the word "Bona" (palare for "good"). He would enter by saying, "Hello, anyone there?", and Julian (Hugh Paddick) would answer, "Ooh hello! I'm Julian and this is my friend Sandy!"
Here is a quote illustrating the use of double entendre from the sketch "Bona Law", featuring Julian and Sandy as lawyers:
At other times, Horne's character would pretend not to understand the more risqué meanings in Julian and Sandy's dialogue, although it was always hinted that he was secretly in on the joke.
The sketches also often had Horne drawing out of Julian and Sandy more about their personal lives than Horne was seeking, as the two would misunderstand his meaning. In one sketch, discussing Julian and Sandy's time out travelling the world aboard ship, Sandy reveals Julian was swept overboard in a storm:
In the last episode of Series 4 (which later turned out to be the last ever episode, due to Horne's untimely death) Julian and Sandy are revealed to be "married" — to a pair of "dolly palones" named Julia and Sandra.