When The Avengers was bought by the ABC network in the United States in 1966, network executives were concerned that the audience might not take to the show if it didn't understand the characters, so they commissioned a short introductory sequence to fill in the perceived gap. The sequence was only ever broadcast in the USA, so when Canal+ remastered the episodes, it was omitted from the DVDs produced for the US market. A&E and Canal+ were surprised at the uproar this caused, so when the Emma Peel episodes were repackaged after the Ian Hendry episodes came to light, it was included as a feature on the disc. (thetvdb.com)