Hans's "heil Hitler" response is not, as is commonly thought, "klop!", but is in fact "'tler!", as he is too lazy to recite the two full words of the phrase.
Source: Comedy Connections - S04E06 - 'Allo 'Allo!
Aside from the pilot, none of the episode titles were publicised at original transmission.
A segment of the 'Allo 'Allo! stage production involving an inflatable Hitler - then playing to sell-out audiences at the London Palladium - was filmed and broadcast as part of A Night Of Comic Relief 2, on Friday 10th March 1989.
'Allo 'Allo! is often - incorrectly - described as being devised as a spoof of the BBC's serious war drama Secret Army. In fact, whilst 'Allo 'Allo! did later spoof elements of that and other titles, Jeremy Lloyd first suggested the idea that became 'Allo 'Allo!, having never seen Secret Army. He had been working in the United States during its lifetime. Rather, 'Allo 'Allo! was a spoof of the entire genre of deadly serious, dramatic war films and television series.