The Hoops midfielder began the demolition when his shot was deflected into his own net by Perth midfielder Liam Craig in the 28th minute and four minutes later Commons grabbed number two with another drive before setting up Gary Hooper for number three before the break.
The Scotland international scored from the spot 10 minutes into the second half to begin an argument of whether or not that was his hat-trick before substitute Charlie Mulgrew, on at the interval for Hooper, completed a night of misery for the hapless McDiarmid Park men when he made it 5-0.
St Johnstone's shock 2-1 win against Celtic in the SPL in September was the second of an eight-game unbeaten run which they brought with them to the east end of Glasgow.
However, Celtic recovered from defeats to Barcelona and Kilmarnock in fine style by sweeping away a Saints side who looked a sorry outfit by the time the Hoops, and especially Commons, had finished with them.
Neil Lennon made five changes for the game with Mikael Lustig, Scott Brown, Victor Wanyama, Tony Watt and Hooper coming into the side which lost 2-0 against Killie on Saturday.
Miku, James Forrest, Adam Matthews, Beram Kayal and Mulgrew dropped out, the latter three starting on the bench.
Saints showed two changes with David McCracken and Kevin Moon in for Frazer Wright, out with a broken nose sustained in the 1-1 draw with Inverness at the weekend, and Nigel Hasselbaink, who was named among the substitutes.
The home side had closed the top tier of their 60,000-capacity stadium and the bottom section was far from full but Commons did his best to entertain those who had braved a miserable night.
His personal duel with Alan Mannus began in the 10th minute when the Saints keeper pulled off a good block from the Parkhead playmaker's long-distance drive, before making an easier save when Commons tried to curl the ball past him moments later.
With the Perth side doing little offensively aside from launching long balls to lone striker Gregory Tade, Celtic continued to dominate possession.
In the 21st minute, after Saints midfielder Murray Davidson had bundled Hooper to the ground 30 yards from goal, Commons's deflected free-kick caused Mannus some trouble before the Perth keeper grabbed the ball at the second attempt.
Moments later the St Johnstone number one was again forced into a save from Commons's 30-yard drive, the wobbly Saints defence smuggling the ball out the box after the keeper had spilled it.
The former Nottingham Forest and Derby player had yet another attempt from outside the box and this time his shot went wide of the far post.
Commons eventually got the breakthrough albeit with the help of Craig whose attempt at blocking the angled-drive succeeded only in taking the ball past Mannus and into the roof of the net.
There was no doubt about Celtic's second goal which followed soon afterwards.
Lustig's pass from wide on the right found Hooper who quickly played in Commons and he drilled his shot low past the helpless Mannus from 12 yards.
Steve Lomas's men looked sapped of all belief as Celtic piled forward at will. In the 38th minute Lustig had a header cleared off the line by Steven Anderson after McCracken had inadvertently headed off his own crossbar.
However, a minute later the tie was effectively over when Hooper, in typical poacher's fashion, was on hand to knock Commons's pass past Mannus, who was left exposed once again.
Mulgrew replaced the former Scunthorpe striker for the start of the second half while Steven MacLean came on for Rowan Vine but there was no way back for the visitors.
In the 56th minute Celtic were awarded a penalty when Anderson fouled Watt and Commons, almost inevitably, stepped up to slam his spot-kick past Mannus.
It had become a matter of how many Celtic would score and just after the hour mark Mulgrew made it 5-0 after more indecision in the ragged McDiarmid Park defence had allowed the Hoops utility player to find a yard before shooting into the far corner.
The shell-shocked visitors were all over the place and there was a moment of farce when McCracken almost put the ball into his own net trying to usher a Watt cross away from Mannus.
Celtic kept pushing for more goals but five minutes from time, Hasselbaink, on for Tade, struck the outside of the post, depriving the visitors of a consolation goal.