IF this is what happens when we allow them to spend too much time in each other's company then maybe we should try it more often.
Scottish football's delinquent twins collided for the fourth time in two months at Parkhead last night and by the time they had been pulled apart again a mushroom cloud was hanging over the East End of Glasgow.
This was more than just a cup-tie, more than just another 90-minute visit to the Old Firm madhouse too. This was the kind of eye-popping, vein-bulging coming together that really ought to earn these two an ASBO.
And athough some of the on-field behaviour - not to mention some of the off-field stuff - was appalling, you just couldn't take your eyes off it.
In the end, Mark Wilson's second-half strike was all that separated them and enough to take Celtic into a quarter-final trek north to take on Caley Thistle.
It also kept alive Neil Lennon's dream of a remarkable first season treble.
But that's only half the story. And the result was half expected in any case, especially given the state of a Rangers side that arrived across the city at its most threadbare.
It was how the teams arrived at this conclusion that caused all of the drama.
Rangers were reduced to 10 men in the first half, then nine in injury time, then eight before they had made it into their own dressing room.
But it wasn't just Steven Whittaker, Madjid Bougherra and El Hadji Diouf who saw red.
On the final whistle Lennon and Ally McCoist - the two men who will go head to head as managers next season - had to be stopped from going for one another's throats.
Lennon's assistant, Alan Thompson, wrapped two arms around his manager to keep him from McCoist who stood at the mouth of the tunnel looking for his man.
Meanwhile, in the centre circle, Diouf was rounding on referee Calum Murray who, despite having already called time on this mayhem, then produced a third red card to send the Senegalese packing too.
This time Rangers had not gone down without a fight the way they had 10 days previously.
But Celtic landed the knockout blow - and they were worth it too.
Lennon's side had a formidable look as these two old rivals emerged together into a heaving, floodlit cauldron. The place crackled with electricity at kick-off time to such an extent it seemed to have taken on a pulse of its own.
This was a living, breathing bear pit. And the madness hadn't even started.
Celtic swarmed all over Rangers at first, tails up and feeding off the energy around them.
Georgios Samaras frightened the life out of Bougherra when he forced the Algerian into a anxious clearance and then, in a glimpse of derbies past, Gary Hooper got a run on Davie Weir but this time Richard Foster raced back to make a critical penalty box tackle.
Still, Celtic were once again flexing their muscles and seizing control.
Scott Brown and Diouf also renewed their personal hostilities inside the first 15 minutes when the pair snarled at one another during a brief break in the play. It was all breathless stuff.
Moments later, though, the place fell silent when Diouf got in behind Celtic's defence and forced Lukasz Zaluska to come charging off his line in a race he never looked likely to win.
He did do just enough though to half block Diouf's cross and Daniel Majstorovic brought the noise levels back up to "ear bleeding" with the clearing header.
Ki Sung-Yueng would have blown the roof clean off in the 22nd minute had his 35-yarder ripped into the roof of Allan McGregor's net rather than clear the keeper's crossbar by a couple of inches.
But Celtic were not having everything their own way. Without managing to get forward in any great numbers, Rangers were at least beginning to find their feet and win their share of tackles in midfield, stemming the green-and-white flow towards their own net.
Whittaker went into referee Murray's book in 28 minutes for adopting a thou shalt not pass approach to stopping Ki from getting into another dangerous area.
Murray, it must be said, appeared the calmest man on the park, which, amidst all this raw testosterone, took some doing.
He also correctly carded Majstorovic soon after that when the burly Swede launched into a lunge on Diouf.
But this one was only just warming up. In 37 minutes, it reached boiling point.
Whittaker went in shin high on Emilio Izaguirre, leaving the Honduran star writhing in agony. Murray had no choice but to reach for his red card... and light the blue touch paper.
Before Whittaker had even made it up the tunnel, Diouf and Lennon were going nose to nose on the touchline after the Rangers striker had bumped into Celtic's physio.
The sight of this particular pair going at each other was enough to turn the mayhem into complete madness.
Murray waded into it to book Diouf who then angrily demanded action be taken against Lennon.
This was eventually done, on the advice of fourth official Iain Brines, who also advised Murray to give McCoist a ticking-off before play could resume.
When it did, Samaras bundled his way through only to be denied by McGregor's brave save. This was as close as either side would come to a first half goal.
But by this point the game was a mere sideshow to the real event.
Brown was booked next after catching Weir late. Then Fleck saw yellow for doing the same to Beram Kayal.
With so much bad blood between them, it was inevitable then, that these two sides would not make it inside at the interval without some sort of skirmish.
Diouf started it by snarling again at Brown. Foster barged between the pair to keep them apart and then, as more bodies piled in, Kyle Bartley and Celtic coach Johan Mjallby went chest to chest.
It was something of a relief then, that all 21 players re-emerged into sight for the second half. Fleck was the only man to stay inside but only because his place had been taken by Kyle Hutton.
If Hutton thought he was being thrown into a melting pot, he didn't know the half of it.
Just three minutes in, the youngster galloped across his own 18-yard box in an attempt to close down Wilson as the Celtic full-back stepped on to Izaguirre's deep cross.
Wilson got there first and smashed a ferocious first-time shot back across McGregor. Papac bravely put his head in the way to make a goal-line clearance but Wilson reacted first to try his luck on the rebound. This time his volley smashed down into the turf and spun up over McGregor as it looped into the net.
Sasa Papac was also in there, out cold and unable to continue.
Rangers - already one man light - were down to the barest of bones and Celtic's attack dogs were sizing them up.
On to replace Papac at full-back came more fresh meat in the shape of teenage winger Gregg Wylde. No sooner had he arrived than Bougherra was having his name taken for a foul on Kayal.
But Rangers continued to hang on in grimly. This was becoming a display of extraordinary resilience even by their standards.
Samaras could have killed them stone dead when he raced on to a magnificent Brown pass, outstripping Bartley for pace but then smashing a low shot back off the base of McGregor's left-hand post.
There had been an anxious moment for Celtic keeper Zaluska, shortly after Wilson's strike, when Charlie Mulgrew headed Hutton's cross high up into the night sky and looping towards Celtic's net. But the big Pole got back in time to save.
That apart, Zaluska's goal hardly came under any serious threat until injury time when Diouf, of all people, lined up a free-kick from 30 yards. The keeper saved then launched the ball upfield to Kris Commons.
Bougherra got back to make the challenge and although he thought he had won the ball, ref Murray blew for the foul and then whipped out a second yellow card to reduce Rangers to nine.
Then, on the final whistle all hell broke loose between Lennon and McCoist and also Diouf and Murray.
And guess what? We've still got another two of these games to go.
