I was slightly taken aback when I heard the news - it's an extraordinary appointment, but it's quite an exciting one as well.
Keegan returns to the club he managed in the mid 90's
They tend to appoint from the heart in the north east and they have done it again.
Obviously the first time he was given the role at Newcastle he had been out of a job for seven or eight years and this is a similar sort of sabbatical.
One thing you know about Keegan is that he is very good at getting what he wants. He makes boards listen and react in terms of the investment they put in and the people he wants.
He's got a big pulling factor up there and he's hugely popular. He was great as a player, wonderful as a manager - almost winning the league title - and I think the fans would 'love it' if he pulls it off this time.
It's great for the Premier League as well as Newcastle, it's an exciting appointment. We know the type of football he likes to play - it's pretty cavalier - and the fans like that type of stuff.
But ultimately they want a piece of silverware. It eluded him before but can he manage it this time? I think it will take him time because the side is not the strongest.
They've got the nucleus of something but they need a bit more; they're certainly a long way short of the side he left at Newcastle some years ago.
Gary Lineker was speaking to BBC News 24.
Match of the Day pundit
It's great for Newcastle.
The last time Keegan was manager he took them from total obscurity to nearly winning the Premier League and gave them a brand of football that was just unbelievable.
When he was there they played in some of the best games the top flight has ever seen, he's a legend at Newcastle and I think he will do really well for them.
I thought he wouldn't come back at all but the lure of Newcastle, where he had a fantastic time as a player and a manager, was too much and it's one of the few clubs he would have gone back to.
The Newcastle fans demand not only winning, but winning in style and Keegan gave them that. I think he was one of the reasons why a succession of managers failed because it was very difficult to play the same way and keep on winning.
Supporters go to the home games wanting 5-3s and 5-4s that they got under Keegan but it will be very difficult to go back and emulate that. However, I'm sure he is looking forward to the task.
All the Newcastle fans will love him there. If Alan Shearer wasn't going to take the job then the one guy that could go back with the full support of the supporters is Kevin Keegan.
Alan Hansen was speaking to the BBC.
Match of the Day pundit
My reaction to Kevin Keegan is always a positive one - I've played for him, I was his captain and I had success with him.
Keegan is a Newcastle hero as a player and as a manager
He's a great manager to play for, he inspires players and fans and will capture the hearts of the supporters once again.
The difficult thing is that it's always more difficult second time. But the club are at a low ebb and maybe he's looked at the situation and the chairman, who's a fan with money to spend, and thought "this is the time I could make a difference".
With Kevin, there's a track record as a player and a manager, so the fans know his qualities and with any kind of quality that's proven in the past, it'll come again.
Kevin's nothing if not brave.
He likes to take on a challenge, maybe he looks at it and thinks "not many have gone back and succeeded a second time", in the same way that not many had gone abroad when he went to play in Hamburg.
He doesn't dwell on negatives, he enhances the positives and at the same time, with the experience he's gained over the past 15 or so years in management, he'll be able to assess things with a wiser head and see what needs improving.
The game may have changed in certain ways but the characteristics that make up a winner never do, and he has them in abundance.
It's the same with being a leader of men - anyone who's got that, even when he's been out for a while, can still lead people.
I see him being in no way out of touch.
He says he's not watched much football when he was out but last time he went to Marbella for seven years and played golf and tennis, and within two or three years, he'd taken Newcastle to second in the Premier League, so I think that says it all.
Gavin Peacock was speaking to BBC Sport's Julian Shea.
Match of the Day pundit
I'm not surprised by this appointment.
The Newcastle fans just want to be entertained and the best Newcastle have played in the last 20 to 30 years is under Kevin Keegan.
The majority of fans up there have a different mentality. They earn their money, buy themselves a season ticket - 50,000 of them - and they just want to be entertained every week and under Kevin that is the way it was.
Newcastle aren't going to be relegated this year, they're not going to reach Europe either so he's got a five-month run at it.
That allows him to have a look at the players, what he needs, and look around to see who he can sign in the summer. I'm sure he'll get fantastic backing from owner Mike Ashley.
He will motivate the dressing room. I've played with a lot of managers, worked with quite a lot of people in football and I've sat through some of his team-talks, both before the game and the inquest afterwards.
You would very much put your boots on and play for that fellow because he believes in you so he's very good at that side of the game.
He's not the greatest of coaches - he would admit that and will get people in to do that job for him.
But in terms of motivation, man management and players playing for him then he will be absolutely spot on.
Mark Lawrenson was speaking to BBC Radio 5 Live.
BBC Radio 5 Live pundit
It is quite an unbelievable appointment.
I played with Kevin as a player and he was very enthusiastic and passionate about the game.
As a manager he realised what the fans wanted - they loved exciting, entertaining football. He gave them that and signed some wonderful players at St James' Park, it really was a rollercoaster for five years.
He's got to put some confidence in the team. He's a very positive fellow and that's one of his strengths as a manager - let's be honest, people don't think about his teams as tactically solid.
It's an interesting time for him to come back. It's very flat at Newcastle at the moment and there's not a lot of buzz about the place.
Players look at wages but they like to play for a manager who has got a lot of passion, a lot of desire, and Kevin Keegan is a very big name in the world of football.
Everyone thought he would call it a day and that was probably the end of it, but if there's any club where his loyalties lie it is Newcastle.
He's got terrific backing there with the supporters who've always loved him, and it's brought him out of retirement.
Hopefully his batteries will be recharged and he's got a lot of work to be done.
It looks like happy days again at St James' but he needs to be given time, it is going to take a while.
Chris Waddle was speaking to BBC Radio Newcastle and BBC Radio Five Live.
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