A blooper, also known as an outtake, is a moment in the recording process of a piece of media in which a mistake occurs that ruins a take. Such common mistakes to occur in these circumstances range from actors forgetting or stumbling over lines, breaking or falling out of character (known in the theatre business as "corpsing"), issues with props, or unintended intervention from the production crew. General instances of cast and crew messing around on set is also a common feature.
These productions typically make no secret of these failed takes, and it is common for a "blooper reel" to be put together for home video releases, as many of these errors result in humorous situations. Blooper reels are, indeed, a reoccurring bonus feature on home video releases of Doctor Who media.
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