Rhyno Smith scored twice in the closing stages against Southern Kings to again secure the bragging rights for the Cheetahs.
Exeter Chiefs rallied in the second half against Sale Sharks, but the Premiership leaders still slipped to a first defeat since November.
Northampton Saints looked to be heading top of the Premiership until London Irish sprung a shock following Api Ratuniyarawa's dismissal.
At the end of another week of crisis, Saracens had rare cause for cheer as they reached the quarter-finals of the European Champions Cup.
Northampton Saints and Glasgow Warriors did all they could to stay in the European Champions Cup, while Ulster are definitely through.
A thrashing of Lyon ensured Leinster made it five wins from five in the European Champions Cup, while Racing 92 reached the last eight.
Rhys Carre's early red card made life difficult for Saracens, but they still defeated Ospreys in the European Champions Cup.
La Rochelle kept their hopes of progressing in the European Champions Cup alive by beating Sale Sharks, while Harlequins edged out Bath.
Stade Francais came into the Clasico sitting bottom of the Top 14, yet they pulled off a thrilling win in Paris as Toulouse wilted.
Sam Hill and Gareth Steenson starred for Exeter in their win over London Irish, while Taqele Naiyaravoro was the hero for Northampton.
High-flying pair Lyon and Bordeaux Begles celebrated contrasting victories in Top 14 action on Saturday.
Ospreys were boosted by George North's return but still could not see off Dragons in Pro14.
Five tries in each half saw Premiership basement side Saracens make light work of thumping Worcester Warriors on Saturday.
Ulster maintained their unbeaten home record in the Pro14 with an emphatic win over Munster, who slipped off the top of Conference B.
It was a night to forget for Harlequins on Friday, as they were thrashed by a rampant Sale Sharks side in Premiership action.
Bordeaux-Begles are back at the top of the Top 14 and increased their advantage over Toulon and Toulouse.