These are brilliant!
I was on a packed commuter train years ago, and right beside 2 women, who were obviously work colleagues. It was clear very soon exactly who they worked for, and the older of the 2 women then proceeded to slate practically everyone she worked for. This being Ireland it's a totally daft thing to do, as there is a REALLY high likelihood of someone connected overhearing.
Anyway, the second of the women who was younger, clearly couldn't stand Older Colleague. I was listening with rapt interest, as Older Colleague kept bitching about ever increasing numbers of colleagues and whatever mild comment Younger Colleague made, she'd say something snotty or withering back.
Older Colleague moved onto an ad that was on the time for Miwadi orange juice. The tag line was the young boy in the ad saying 'It's not YOUR miwadi is MIWADI'. Older Colleague was boasting that the boy was her nephew. Younger Colleague was clearly so pissed off that she feigned ignorance of the ad. Ever more hysterically, Older Colleague kept screeching, 'but you do know him, you do know Jack [boys name apparently' and repeating the tagline, to Younger Colleague's insistence that, no, never heard of him / ad etc.
I was totally engrossed in the whole thing at this stage, and after many 'but you DO know him, you know Jack' comments from Older Colleague, I completely forgot I wasn't meant to be listening and yelped 'I know him! I know Jack'. The 2 women just stopped & stared and I had to stand pressed beside them for another 3 or 4 stops. Mortified.
(I still love listening to people's conversations when I'm out. I once actually got off the bus early as I was so invested in a story I was listening to).