The pair arrive on her doorstep on Boxing Day, and Karen (played by Lorraine Stanley) quickly jumps to conclusions when Mitch (Roger Griffiths) and Kandice (Hannah Spearritt) are hoping to surprise her.
But spoiler pictures have revealed how Karen acts quickly when she thinks they are having an affair.
The Taylor matriarch, in true Karen style, ends up chucking trifle on the two of them.
Kandice and Mitch are both pictured ducking for cover as sponge fingers are launched towards them from the flat window.
Another snap shows Kandice covered in cream after Karen throws the dessert at her.
But what do Kandice and Mitch have in store for Karen?
Karen actress Lorraine has spoken out on the drama as she revealed: “I don’t want to give too much away but Mitch and Kandice are planning something and Karen being Karen comes to all sorts of assumptions and puts two and two together and gets five.”
She also elaborated on why her character has such a tense relationship with her younger sister at times.
Lorraine added: “Kandice has always gone after Karen’s boyfriends in the past so I think the tension comes from when they were really young.
“Also, Kandice is such a snob, and Karen really tries her best to keep up appearances, but Kandice always manages to find fault.”
The last time Mitch showed up in Walford, he ended up disappointing his son Keegan (Zack Morris) as he disappeared on him again.
Mitch found money posted through the door that was meant for Ted Murray (Christopher Timothy), but he helped himself to the cash.
But what has Mitch been up to since he’s been away?
Keegan has been through an incredibly tough year, and his dad has been nowhere to be found.
Keegan star Zack has divulged that his character isn’t too happy to see his old man.
He spilled: “As you can imagine he’s not very happy about it, it’s a mixture between confusion and just frustration really.
“Last time Mitch was there they started to rebuild their relationship, and it was the kind of relationship Keegan always wanted.
“Then, as soon as it started going well and he started to trust Mitch again, he suddenly left.
“Mitch did what he always does, but Keegan had put his guard down – he didn’t think his dad would do it to him again, but he did.”
EastEnders continues tomorrow at 8.30pm on BBC One.