For anyone not familiar, Kat is a character played by Jessie Wallace and she (her character) will tell her ex-husband, played by Shane Richie, that she's expecting a child in a gripping Christmas storyline.
It's the first baby for the couple, who have reunited after 11 months apart.
Last month, fans of the BBC 1 soap watched Alfie have second thoughts about his feelings for lover Roxy Mitchell (Rita Simons) - despite saying 'I do' at the church and signing the register.
Kat – who shared a passionate kiss with Alfie on the night of his stag do – briefly showed up at the wedding but then left without saying a word.
Alfie ditched Roxy in a bid to chase after his former flame who was boarding a flight to Ibiza, and the couple got back together.
Got that? Good.