Peterborough United signed striker Craig Mackail-Smith for a third time.
The 32-year-old has re-joined Posh on loan from League Two side Luton Town for the rest of the season.
He is stuck on 99 goals for Peterborough and will be hoping to bring up his century in his latest spell at the ABAX Stadium.
Mackail-Smith has struggled to break into the Luton team this season, with manager Nathan Jones going for other options up front instead.
I am delighted to have him. I feel as if the squad need one or two older heads and he brings that.
He also has a real passion for this football club, you can't buy that. I feel like Craig has a point to prove.
Meanwhile, 19-year-old striker Freddie Hinds has joined Championship side Bristol City for an undisclosed fee.
Peterborough United chairman Darragh MacAnthony has told fans on social media that the club are expecting a quiet deadline day tomorrow.
Posh have seen their form dip dramatically in recent weeks, conceding 11 goals in their last four games, but MacAnthony is refusing to panic.
When asked by one supporter on Twitter whether a busy 24 hours was in store, MacAnthony replied that it will be "very quiet".
Watch Donovan Blake's interviews with MK Dons boss Robbie Neilson and Peterborough manager Grant McCann.
Robbie Neilson hailed the victory over regional rivals Peterborough as a "strong performance".
The MK Dons boss said he was delighted by way his team played and singled out Chuks Aneke for praise.
"He's been fantastic in the time I've been here, he's had a really tough year, he's been building his fitness back up. I think you could see the spirit in the team and the regard they hold him in, and the way they went to celebrate with him after his goals. It was great for him, he's a great kid."
Peterborough manager Grant McCann was left frustrated. Saying his team 'just folded' after going behind.
Peterborough United's Shaquile Coulthirst has joined League two side Mansfield Town on loan.
The former Tottenham Hotspurs striker joined Posh last January on a three-and-a-half year contract for an undisclosed fee.
He's scored seven goals in 43 appearances in all competitions since making the move to the ABAX Stadium.
The 22-year-old joins Mansfield until the end of the season with the option for a permanent move in the summer.
League One Peterborough United couldn't produce an FA Cup shock at Premier League leaders Chelsea.
First half goals from Pedro and Michy Batshuayi gave Posh the proverbial mountain to climb at Stamford Bridge, a task which got tougher when Willian made it 3-0 after the break.
Chelsea had John Terry sent off before Tom Nichols gave Posh fans something to cheer by scoring with 20 minutes left.
But Pedro ended any hopes of a dramatic comeback by scoring his second and Chelsea's 4th.
Around 6,000 Peterborough supporters watched the game in West London, while many more followed the action on a big screen at their home ground the ABAX Stadium.
Peterborough United supporters were in optimistic mood as they dreamed of an Emirates FA Cup upset at Premier League leaders Chelsea.
Posh will have around six thousand fans at Stamford Bridge plus many at their own ground, the ABAX Stadium, watching the Third Round contest on a big screen.
A fleet of coaches took a large proportion of Peterborough's travelling support to West London at mid-morning.
Although Peterborough have lost both their previous FA Cup encounters against Chelsea - conceding five goals on each occasion - followers of the League One promotion chasers are determined to enjoy their day out in West London.
And many have the same hope as the club's Director of Football, Barry Fry- to hold Chelsea to a draw and earn a money-spinning replay at home.
"I've been in football for 56 years and it's the first time I'm going and wanting a draw. I've never wanted a draw. But this one, it would be lovely to get them back at our place."
Peterborough's Barry Fry talks about his hopes for their FA Cup game at Chelsea.
Peterborough fans give their pre-match verdicts before setting off to Stamford Bridge
Peterborough's tie with Chelsea is the pick of the region's FA Cup Third Round clashes this weekendRead the full story ›
Peterborough United have completed the loan signing of Rotherham United defender Dominic Ball on a deal until the end of the season.
The 21-year-old started his career at Tottenham Hotspur and spent much of last season out on loan at Rangers.
Ball has been given permission to feature in Sunday's FA Cup tie at Chelsea
It is great to have Dominic at the club. He has good experience, he won the league last year with Glasgow Rangers in a loan spell and we are delighted to have him here.
It is an extra option for us defensively, he can play at centre back, full back or in the holding midfield role, so it is great to have that versatility.
Peterborough United have re-signed West Ham midfielder Martin Samuelsen on loan until the end of the season.
The 19-year-old Norwegian was a fans' favourite during his time at Posh last season and scored a memorable solo against Sheffield United at Bramall Lane.
He joined Championship side Blackburn on loan earlier this season but failed to make an impact at Ewood Park.
Delighted to confirm @samuelseen has rejoined us on loan for the rest of the season. Compliments our squad perfectly & lads all thrilled!
Samuelsen is eligible to face Scunthorpe United tomorrow and will also be allowed to play in the big FA Cup tie at Chelsea next Sunday.
It is great to have Martin back at the club.
He is well loved by the players and the staff and of course the supporters, I am sure he will bring a lot more quality to us and we are looking forward to working with him again.
Meanwhile, on loan George Moncur has returned to Barnsley and defender Ricardo Almeida Santos has moved to Barnet for an undisclosed fee.
Elsewhere, on loan MK Dons winger Ryan Colclough has been recalled by Wigan Athletic.
Peterborough United fans have started snapping up tickets ahead of their big FA Cup tie at Premier League leaders Chelsea next month.
Posh booked their place in the third round after beating Notts County earlier this week.
It's believed the tie at Stamford Bridge on January 8th could be worth at least £500,000 to the club.