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All answers having "Look-alikes" as clue:

4 Character Answers:

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PEAS



5 Character Answers:

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TWINS



6 Character Answers:

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CLONES

IMAGES



7 Character Answers:

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RINGERS



13 Character Answers:

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TWOPEASINAPOD



23 Character Answers:

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TWEEDLEDUMANDTWEEDLEDEE