Jennifer Aniston's most iconic role is now also a big trigger for her -- a question about the "Friends" anniversary made her break down, as she's still reeling from Matthew Perry's death.
Jen sat down for a conversation with "Abbott Elementary" star Quinta Brunson to discuss their craft for Variety's "Actors on Actors" series ... but, the convo took an emotional turn when Quinta set up a question about the classic sitcom turning 30.
Check out the clip ... as soon as Jen heard what was coming she whispered, "Oh God, don't make me cry." That reaction then made Quinta start tearing up ... and both women shared a moment as they tried to avoid bursting into a full cry sesh.
Quinta offered her an out, but JA said she does want to talk about the show, and added, "I'm sorry, I just started thinking about ..." -- although she cut herself off, she was clearly thinking about Matthew.
Jen pulled through, and as she dabbed her eyes, she called them "happy tears."
Then she shared some old memories, including having lunch with Matthew on the day the show premiered almost 30 years ago.
TMZ broke the story ... Perry was found dead IN his L.A.-area home last fall -- with the coroner determining acute effects of ketamine caused his death.
There's another wrinkle, however ... law enforcement sources recently told us local police and the feds are now investigating the source of the ketamine -- trying to figure out how the actor, who struggled with addiction for many years, got his hands on it.