Laing, 30, injured himself during filming for Saturday night's pre-recorded launch show and was forced to pull out of the competition.
Fletcher, who is best known for playing Andy Sugden on the British soap, was paired up with professional dancer Oti Mabuse.
The other 14 celebrities were also paired with dancing professionals, including reigning champion Kevin Clifton, who will dance with Anneka Rice.
Rice cast doubt on whether her partner would be able to win for a second year running. “I haven't got a rhythm gene, I can't even clap in time,” she joked.
The launch show on Saturday 7 September also saw the debut of new judge Motsi Mabuse, who is Oti’s sister.
Strictly Come Dancing begins on 21 September.
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