Denise will be making her screen debut on the soap next month, where fans will see Karin cause a stir among the male residents of Walford.
Karin turns up looking for Phil Mitchell, but once she catches the eye of love rat Max Branning, he invites her into his portacabin, and she "offers him something he can't refuse".
But the producers tease, "is all what it seems?"
It was announced in February that Denise would be joining the BBC One soap for a short stint.
Denise told the Daily Express last month: "I'd been asked before to go on but the timing was never right – I was pregnant or there was another reason.
"But it is the 30th year which for me was a no brainer. If I am ever going to do it, it has got to be now - I've grown up with the show."
Meanwhile, executive producer Dominic Treadwell Collins previously said: "It was only a matter of time before Denise Van Outen walked onto the Square. We cannot wait to have Denise join us for a few episodes - where she will definitely make her presence felt..."
Denise's entrance as Karin Smart can be seen on 9 April 2015.
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