Champions League games: The eight most shocking moments throughout history
This season has already thrown up some moments that will stick in the mind, from Manchester United's non-existent defending in Istanbul, to both sets of teams walking off the pitch in Paris when Basaksehir faced PSG.
But Europe's premier club competition has seen some other shocking moments down the years, from match-fixing scandals to harsh red cards and significant referee abuse.
Ahead of the return of the action tonight, Sportsmail goes through the list of the most shocking moments in Champions League games history...
LUIS GARCIA'S GHOST GOAL AGAINST CHELSEA, 2005
Liverpool's 2005 Champions League-winning campaign was filled with some iconic moments - the Istanbul comeback and Steve Gerrard's last-gasp wondergoal against Olympiakos to get them out of the group stage to name a few.
But there is a major controversy that puts an asterisk on their success. In the opening minutes of their semi-final second-leg clash against Chelsea, Milan Baros was sent clean through on goal by captain Gerrard at a raucous Anfield
The Czech striker nudged the ball past Petr Cech, and a covering John Terry appeared to stutter as he attempted to clear, allowing Luis Garcia to nip in and prod the ball towards goal.
William Gallas made a valiant effort to salvage the situation, and got to the ball before it had crossed the line. Or had he?
Luis Garcia wheeled away, convinced he had opened the scoring. That was enough for the officials, who gave the goal, to the delight of Anfield and the dismay of those in blue.
Replay after replay only served to deepen Chelsea despair. In reality, it wasn't even close.
It was the deciding goal in the semi-final across the two legs, leaving Jose Mourinho's Premier League champions livid and Rafa Benitez's men one step away from a place in Champions League folklore.
ROBIN VAN PERSIE'S RED CARD VS BARCELONA, 2011
Arsenal were leading FC Barcelona on aggregate in the last-16 2011 after Sergio Busquet's own goal cancelled out Lionel Messi's opener at the Camp Nou.
The Gunners had beaten the Catalans 2-1 in the Emirates Stadium first-leg and were looking to complete a shock triumph.
In the 56th minute, Robin Van Persie had a chance to put the tie beyond the reach of Pep Guardiola's men, but the opportunity was cut short by the linesman's flag.
The Dutch striker pulled the trigger anyway, unaware that play had been brought to a halt.
Massimo Busacca,who was the chief official that night believed Van Persie was trying to waste time in putting the ball into the stand,an act he deemed punishable by a second yellow card.
The Dutchman protested his innocence, insisting that he didn't see the flag go up nor did he hear the referee's whistle over the din made by 90,000 people sat in the Camp Nou.
His claims fell on deaf ears,which caused 10-man Arsenal to conceded twice to end their race for the Champions League Title that season.
Arsene Wenger was furious at the decision, with him and Samir Nasri receiving one-match bans for their post-match remarks against Busacca.
LEGIA WARSAW FIELD INELIGIBLE PLAYER TO HELP CELTIC, 2014
Polish side Legia Warsaw thumped Celtic 6-1 on aggregate in the Champions League third-qualifying round in 2014. A 4-1 first-leg loss was compounded by a 2-0 defeat in Scotland, with the Scottish champions having to settle for a spot in the Europa League.
With the tie all sewn up, Legia brought on Bartosz Bereszynski as a substitute in the dying minutes at Celtic Park.
There was only one slight hitch - Bereszynski was supposed to be suspended after getting a red card for violent conduct in the previous season's Europa League.
Celtic spotted the gaffe and reported it to UEFA, who awarded the Scottish champions a 3-0 win for the second-leg which put them through on away goals.
Even more galling though for both was Celtic's failure to take advantage of their reprieve.
Ronny Delia's men were knocked out by Slovenian side Maribor in the last qualifying round and had to settle for Europa League football in any case.
CHELSEA DENIED PENALTIES IN BARCELONA HEARTBREAK, 2009
Chelsea were leading Barcelona 1-0 on aggregate in the Champions League semi-final second-leg in 2009 thanks to Michael Essien's wondergoal at Stamford Bridge.
The Blues were desperately trying for a second goal to put Pep Guardiola's side to bed, but were getting no help from referee Tom Henning Ovrebo, who refused to give what appared four stonewall Chelsea penalties in west London.
The Norwegian official did not spot that Florent Malouda was fouled in the penalty area during the first-half, instead giving a free-kick outside the area. Ovrebo also missed Eric Abidal pulling Didier Drogba's shirt when the striker was through on goal.
And while the referee did sent Abidal off for a last-ditch challenge on Nicolas Anelka, he also refused to give two clear handballs committed by Gerard Pique and Samuel Eto'o in the second period. After such dismal luck, you could sense what was coming.
Chelsea frustration boiled over into downright anger when Andres Iniesta scored a stoppage-time equaliser to put Barcelona into the Champions League Final on away goals.
The Blues were furious with Ovrebo after the game, surrounding him at every opportunity. Drogba made his feelings very clear to the Sky cameras, calling the Norwegian 'a f****** disgrace' whilst being dragged away by coach Guus Hiddink.
Chelsea fans also threw objects at the referee, earning the club a hefty fine, while death threats were also sent to Ovrebo.
The official later admitted he had made several mistakes and did not referee at the 2010 World Cup finals later that year.
REFEREE ANDERS FRISK RETIRES AFTER CHELSEA MATCH, 2005
After Barcelona's 2-1 Champions League win over Chelsea in February 2005, Jose Mourinho accused referee Anders Frisk of favouring the Spanish side in the match at the Camp Nou.
Frisk had sent off striker Didier Drogba for two yellow cards, while the Portuguese coach even claimed he saw the referee invite Barcelona coach Frank Rijkaard into his changing room.
This led to several Chelsea fans making death threats on the Swedish official, with the supporters phoning, emailing and even sending letters to Frisk.
The irony is that Frisk claims he was a 'Chelsea fan since boyhood' and couldn't understand why his fellow supporters were making these threats.
This caused the Swedish referee to retire, thereby ending a 30-year career in officiating. He went on to receive the FIFA Presidential Award later that year as 'recognition for a career cut short following death threats against his family'.
CHAMPIONS MARSEILLE BANNED FROM EUROPE, 1993
In May 1993, Marseille needed to beat Ligue 1 side Valenciennes to win the league title, before facing AC Milan in the Champions League final six days later.
With the French side facing such an important league match with one eye on the European final, Marseille president Bernard Tapie decided to bribe three Valenciennes players and their manager to go easy on them so they didn't pick up any injuries.
As a result, Marseille went on to beat Valenciennes and Milan to clinch the league and Champions League double in the space of a week. Naturally, though, news of the bribery began to emerge.
The Ligue 1 title was stripped from Marseille's clutches, while they went on to be banned from the 1993-94 Champions League season despite winning the trophy the season before.
Tapie and Valenciennes star Jean-Jacques Eydelie were given jail sentences, while the two other players - Jorge Burruchaga and Christophe Robert - and Valenciennes manager Jean-Pierre Bernès were given suspended sentences.
BUFFON RAGES AS RONALDO STRIKES LATE FOR MADRID, 2018
Italian side Juventus put in a perfect second-leg performance against reigning champions Real Madrid at the Santiago Bernabeu.
Trailing 3-0 from the opening leg in Turin, Max Allegri's side stunned Madrid by netting three goals in an hour to delete the deficit. The Serie A champions were holding on desperately to force extra-time and frustrate Zinedine Zidane's men further.
Yet with 30 seconds to goal, Cristiano Ronaldo knocked a cross-field ball down to Lucas Vazquez, who collapsed in the area after Medhi Benatia's challenge.
Contact was minimal, with the Juventus defender even getting a slice of the ball, but English referee Michael Oliver gave a penalty.
Legendary Juventus goalkeeper Gianluigi Buffon - who is normally so calm and cool in high-pressure situations - lost it. He approached Oliver straight away and started pushing him around, earning him a straight red card.
Wojciech Szczesny came on for the penalty, which Cristiano Ronaldo dispatched comfortably and Madrid went on to retain their Champions League crown later that year.
The drama wasn't over, as Buffon was not done abusing Oliver. In a post-match interview, the goalkeeper claimed the official should be 'sitting in the crowd eating crisps' rather than managing the game.
LUIZ ADRIANO CHAOS IN DENMARK, 2012
Nobody was expecting much drama from the Champions League group encounter between FC Nordsjaelland and Shakhtar Donetsk in November 2012, but boy did it provide some talking points.
Trailing 1-0 in the first-half, Shakhtar winger Willian kicked the ball downfield back to the Nordsjaelland goalkeeper after a drop-ball following an injury, but striker Luiz Adriano did not get the memo.
The Brazilian striker ignored sportsmanship by running on to the long kick and scoring past the Nordsjaelland number one, sparking fury among the Danish team.
Shakhtar then refused to let their opponents walk the ball in the net straight from the kick-off, but Nordsjaelland did manage to retake the lead just a few minutes later.
Luiz Adriano thought he had the last laugh by completing his hat-trick in a 5-2 win for Shakhtar, but he was given a one-match ban by UEFA for a 'violation of the principles of conduct'.
BUSQUETS' CHEEKY PEEK BUT JOSE HAS THE LAST LAUGH, 2010
April 2010. Champions League semi-final. Jose Mourinho vs Pep Guardiola. The last four clash between Barcelona and Inter Milan is a game no-one will forget in a hurry.
Inter came into the match at the Nou Camp 3-1 up from the first-leg but were put at a disadvantage straight away when Thiago Motta put out a hand to hold off Sergio Busquets, causing the Spanish midfielder to go down clutching his face.
Motta was sent-off for violent conduct but the replays shows the midfielder's hand barely touched Busquets' face.
Furthermore, the Barcelona man had a cheeky peek through his hands to check that Motta was being dismissed, implying that he was barely hurt at all.
That gave Barcelona a bit of impetus, but while defender Gerard Pique scored the opener six minutes from time for the Catalans, Inter Milan held on to gain a spot in the Champions League Final that year.
Manager Jose Mourinho burst onto the Barcelona pitch, wagging his finger like a mad man as he went over to celebrate with the travelling Inter fans.
Mourinho's men would go on to win the final against Bayern Munich in Madrid.
TWO OFFSIDE GOALS FOR RONALDO AGAINST BAYERN, 2017
Real Madrid and Bayern Munich competed in a classic Champions League quarter-final clash in April 2017, but the Santiago Bernabeu clash was filled with controversy.
The German champions managed to force extra-time by matching Real Madrid's 2-1 win from the first-leg, but the game turned on its head just before the 90 minutes were up.
First of all, referee Viktor Kassai sent off Bayern midfielder Arturo Vidal for a second yellow card when he clearly got the ball. Then Cristiano Ronaldo struck in the first-period of extra-time, but was standing in an offside position when he was given the ball for his close-range strike.
Ronaldo then made it 3-2 to Madrid by completing his hat-trick, though also looked offside when he was given a simple finish from a Marcelo pass.
The officials made it an unhappy return to Madrid for Carlo Ancelotti.