In the clip, shared before the final stages of qualifying, Cassidy takes a swipe at the Season 2 Formula E champion, asking, "What is he doing?" as they drive on-track.
"Oh, that was really kind of Seb," the Kiwi starts. "Wow, what a good teammate. Ahh, what is he doing, man? Seriously."
Things then took an unusual turn when the man currently sat second in the Drivers' World Championship imitated his Swiss colleague, going on to say, "The guy in front of me, in the debrief, will go 'ah yes Stoffel, I would be P1, but I got traffic. If my mum was a man, blah blah blah'."
Both drivers seemed to be happily chatting away after the radio call was broadcast, and Envision Racing's Managing Director Sylvain Filippi seemed keen to put these rumours to bed.
"We've seen that before," Filippi explained. "When you have the car to win races and championships, the stakes are obviously higher. There's a bit of frustration sometimes. It's our job to calm things down and then make sure they are focused on the job. I would much rather have that and a quick car than the other way round."
Buemi and Cassidy are new teammates for Season 9, but Filippi stressed that they have a good relationship despite Cassidy's outburst.
"The boys get on famously. It's all good. But when the prize is so near, and you can see something exciting, emotions are a bit higher. It's normal to see that in any motorsport.
"But it's our job to ensure that it doesn't harm our performance at the end of the day."
Buemi and Cassidy went up against each other in Duels, with Cassidy setting the quicker time of the two in the Quarters. However, his time was deleted after being found guilty of improper use of the full-power 350kW mode.
"I have been disqualified for changing power mode," Cassidy explained. "You're allowed to change in sector three on your out lap, not before, I think it's worded. I started my lap on a lower power and changed halfway through, which I thought was a bit of a loophole in the rules. I wasn't the only car, but I was picked up on it. We must look at the rules and discuss them. I thought it was allowed; it wasn't. Too late to complain about it now."