EastEnders star Steve McFadden said it only "took seconds" to get back into the old routine with Letitia Dean when she returned to the Square to play Sharon.
Fans will see the pair re-united on Monday August 13 in the first of seven episodes in five days.
Steve said: "I'd heard rumours and I was really excited because we've got so much history and I knew Linda (Linda Henry, who plays his girlfriend Shirley Carter) was going to have a bit of time out so there was a bit of a crossover and you know you're going to work with someone else.
"Obviously because I've worked with her before I knew what I was going to get so I was excited.
"Letitia is quite a contradiction. She's quite grand and down to earth at the same time. She's very showbiz, but she's very straight at the same time so she's a lot of fun.
"It took seconds and we were very familiar with each other and it was just the same like before she left. She hasn't changed at all."
Viewers will see Sharon return to the Square for the first time in more than six years when she seeks Phil's help after jilting her groom at the altar.
They will also see Shirley discover the truth behind Heather's death and take her revenge.
Letitia said her character realises there is "still chemistry" with Phil, but ruled out romance with him or "charm personified" Jack Branning.
She said: "He's funny, he does stuff that makes her laugh, and I think he feels for her a little bit. She really doesn't have anywhere to go. She's at a vulnerable point and it's a case of someone being kind to her. But Sharon's certainly not looking for a relationship - her son's a priority, and getting a job, probably."