In-form Norwich recorded their second thumping home victory in succession, hammering Millwall to give their promotion bid another boost.
The Canaries, who thrashed Huddersfield 5-0 just before Christmas, were far too good for a poor Millwall side and could easily have won this one-sided encounter by a bigger margin.
Early goals from Steven Whittaker and Cameron Jerome, which both followed errors from goalkeeper David Forde, put Norwich in command at half-time before a brace from Johnson doubled that tally. Hooper then ran through unopposed to score his first.
Substitute Jermaine Easter pulled one back for the Londoners.
There was still time for Hooper to add a sixth as the Canaries made it 10 points from a possible 12 to keep the pressure firmly on the sides above them in the Sky Bet Championship table.
Norwich should have been in front in the first minute when a poor defensive header from Danny Shittu let Jerome in. City’s top scorer shrugged off the attentions of Mark Beevers but then, with just the keeper to beat, shot horribly wide.
Clearly full of confidence the Canaries continued to pile on the pressure and had the ball in the net four minutes later, only for Gary Hooper’s close-range effort to be ruled out for offside.
It seemed only a matter of time before the hosts broke through and the opening goal duly arrived in the 13th minute. Nathan Redmond broke down the right, picked out Whittaker, who was cutting inside him, and the defender’s low shot went straight through Forde and into the back of the net.
Things quickly went from bad to worse for the Millwall keeper when he made a complete hash of a routine clearance, hitting Jerome when he had all the time in the world to clear. The striker could not believe his luck and simply slid the ball into an unguarded net.
It should really have been 3-0 before the 20th minute when Jerome raced clean through again, but his finishing was poor, with the effort going high and wide.
The Lions looked shell-shocked but they steadied the ship in the latter stages of the first half. The Norwich defence were at least being kept occupied but a tame free-kick from Shaun Williams, which was comfortably gathered by John Ruddy, was the best the Lions could muster.
Norwich should have wrapped the points up five minutes after the restart when they caught Millwall short at the back after breaking from a corner.
But when Jerome teed up Hooper with a clear sight of goal the finishing was again of an extremely low standard.
Fortunately for the hosts Johnson was around to show how it should be done. Another quick break saw the ball swept wide to the midfielder and he took a few purposeful steps forward before drilling the ball home from just outside the box to make it 3-0.
Johnson then popped up with his second and City’s fourth on the hour mark, sweeping home Redmond’s cross from the right from close range.
By now Norwich were breaking through almost at will and it took a good save from Forde to deny the rampaging Jonny Howson on 65 minutes.
But four minutes later it was five, with Hooper running through unopposed to score after being put through by substitute Wes Hoolahan.
Woeful Millwall got a consolation goal they scarcely deserved three minutes from time when substitute Easter nodded home after Williams’ free-kick had come back off the bar.
But Norwich had the final say with Hooper providing the finishing touch in stoppage time as the Lions were once again torn apart at the back.