In July 2012, a storyline began in the British soap opera EastEnders in which the character Kat Moon, played by Jessie Wallace, embarks on an affair behind her husband Alfie Moon's (Shane Richie) back, with an unknown person. The suspects named were Ray Dixon (Chucky Venn), Michael Moon (Steve John Shepherd), Max Branning (Jake Wood), Derek Branning (Jamie Foreman) and Jack Branning (Scott Maslen). Ray was the first suspect to be eliminated, on 7 August, followed by Michael on 14 September. The mystery man was revealed as Derek in the 20 December episode. Richie dubbed the storyline "Who's Been Sleeping with Kat?",[1] while critics referred to it is "the who-copped-off-with-Kat saga", "Who Banged Kat?", "Who Shagged Kat?" and the "Kat Mystery Lover storyline".
The storyline received a mixed response from television critics. An Inside Soap reporter called it "soap like we've never seen it before" and the magazine's editor, Steven Murphy, said he was "totally obsessed" with the storyline, while Ellie Henman from Heat called it "possibly one of the most gripping" EastEnders storylines. Soaplife called it "boring" and "ill-conceived", and said that Kat's character had been damaged by the storyline. Kate White from Inside Soap found it "hard to have sympathy" with Kat, Sarah Dempster from The Guardian said it was a "tedious" storyline that "nobody cares" about, and Kevin O'Sullivan from the Daily Mirror called it "dreadful", "ludicrous" and "far fetched", citing similarities with a 2009 storyline in which Heather Trott (Cheryl Fergison) gets pregnant by an unknown man. Sophie Dainty from Digital Spy said the reveal was predictable and criticised the show for not explaining why Kat had the affair.