It's not so much as 'overheard' as an experience, but I think it's funny enough to count. There are so many hilarious quotes I don't even think I could choose one.
I went to a little, remote scare park in America one year. It was normally a ski resort, but in October they open haunts. Half of the park was on one side of the car park, while the other was on the other side, with a small pathway and a single maze connecting them. My best friend, her family, my mum and I decided to go, but my best friend's little sister, who was only about 5 at the time, (after braving hanging out by the mazes for most of the night) had had enough and wanted to go back to the car, so my friend's mum and dad was taking her back to the car, leaving my mum, friend and I to do one more maze before joining them. We were walking back to the car when I came eye to eye with a roaming actor who had been disgusting himself in a crowd of terrified girls and had a knife he was sharpening. Thinking back on it, the sharpening sounded terrifyingly real. At this time, I had a real fear of roaming actors, and had trying to stay away (or at least hide my levels of fear) from them for the entire night, but since it was late, and I was tired, I was done. I just legged it at my top speed to the car, which I could see by this point. The actor ran, too, chasing me all the way to the car. Now, at this point, my friend had decided to take a different route, she wanted to get pictures with all the actors, so she started running after the actor, seeing if she could get his picture, but he was dead set on me, so she gave up pretty soon. Anyway, so I leapt in my friend's car, screaming to my friend's family "Lock the doors!! Lock the doors!! There's an actor chasing me!! There's an actor chasing me!!" They didn't believe me. There were a few seconds of me acting completely insane while her parents try to calm me until bam!! The actor leaps up on the car window, banging it, knife still in his hand, switching to the other side of the car after about half a minute. My mum's friend instantly leaps out, screaming at the actor "There's a five year old in the back!!" and trying to shoo him away, meanwhile my mum and friend are just laughing their heads off a few feet back, watching the carnage unfold. According to my mum after, the actor had hid behind another car, and was waiting for our car to pull out, when he realised that we weren't leaving, and decided to come to the car itself. Another hilarious thing was that my friend's dad said on the way home "I was going to role down the window."
But honestly, the most scary and hilarious line from it all came from a few days ago when my mum and I were reminiscing about the entire event. She said "He looked pretty disappointed as he walked away." Shivers me to the core while tickling my funny bone.