Tunisia shocked Nigeria and Burkina Faso edged Gabon on Sunday to set up an Africa Cup of Nations last-eight showdown, while minnows Comoros prepared to use an outfield player as a goalkeeper when they confront hosts Cameroon.
Veteran Youssef Msakni scored two minutes into the second half to give previously unimpressive Tunisia a 1-0 second-round triumph over 10-man Nigeria in Garoua.
Nigerian hopes of levelling were dealt a huge blow midway through the second half when Alex Iwobi, initially yellow-carded for a stamp on Msakni, was sent off after the referee looked at the VAR monitor.
In the first last-16 match, Burkina Faso needed a penalty shootout to eliminate Gabon, who forced a 1-1 draw after extra time having played 56 minutes with 10 men following the red-carding of Sidney Obissa.
Substitute Ismahila Ouedraogo scored to give the Stallions a 7-6 shootout victory after Lloyd Palun had struck the woodwork for the gallant Gabonese in Limbe.
With all three goalkeepers unavailable due to positive Covid-19 tests and injury, giant-killers Comoros will place an outfield player between the posts when they tackle hosts Cameroon in Yaounde on Monday.
Whoever is chosen to don the gloves in Yaounde must face Vincent Aboubakar, the leading scorer so far in the flagship African tournament with five goals in three group matches.
Debutants Comoros, representing an Indian Ocean nation of less than one million people, stunned four-time champions Ghana to reach the second round as one of the four best third-placed teams.
The first last-16 showdown on Monday pits the other debutants, Gambia, against Guinea, who will miss their suspended captain, Liverpool midfielder Naby Keita, in Bafoussam.
In a surprise-riddled tournament, another one arrived just after half-time in Garoua when Qatar-based Msakni put the one-time Cup of Nations champions ahead.
Msakni, playing in his seventh Cup of Nations tournament, dribbled across the edge of the box before unleashing a curling shot that entered the net off the left arm of goalkeeper Maduka Okoye.
Substitute Naim Sliti almost doubled the Tunisian lead with 15 minutes remaining when he fired a shot toward the corner of the net only to be thwarted by a superb two-hand save from Okoye.
Nigeria had a chance to level as time ticked away, but Moses Simon sent a free-kick from just outside the box over the crossbar.
In added time, Nigeria had an even better chance to equalise when substitute Umar Sadiq got behind the defence and fired across goalkeeper Bechir Ben Said only to see his shot trickle wide of the far post.
Burkina Faso appeared to have the victory sewn up in normal time thanks to a first-half goal from captain Bertrand Traore, who had earlier missed a penalty.
Gabon were reduced to 10 men when Obissa was dismissed midway through the second half, but they forced extra time as Adama Guira helped the ball into his own net in the first minute of added time.
Qualification is a huge boost for Burkina Faso as the west African state deals with a jihadist insurgency.
On Sunday, gunfire was reported at army barracks around the country as soldiers staged mutinies to demand the sacking of leading members of the military, prompting fears of a coup.
"It was a crazy game and it was not easy to control our emotions," said Burkina Faso coach Kamou Malo.
"We had chances to kill the tie earlier but that's football. It could have gone either way, but we are delighted with the outcome."
Gabon have never won a Cup of Nations knockout tie, but the Panthers can be proud of the way they battled in adversity to force extra time and penalties after the dismissal of Obissa.
The Panthers go home after a tournament overshadowed by the early departures of star striker Pierre-Emerick Aubameyang and influential midfielder Mario Lemina, both positive Covid cases.
"We tried to make up for losing them but you can't easily replace international-class players like that," said veteran coach Patrice Neveu.