The Art of the Heckle: How tough are comedy crowds at the Edinburgh Fringe?
Ventriloquists, mime artists, sketch shows... a woman eating a light bulb. When it comes to comedy, the Edinburgh Fringe has it all.
But no matter how wild or wacky the act, there's one thing every show needs: an audience.
Learning to deal with a rough crowd is a rite of passage for any aspiring comedian.
During one particularly tough gig at this year's Fringe, Canadian comic John Hastings was forced to kick a heckler out.
"I looked at this guy who was 30 stone and six foot seven," he said.
"And I frankly didn't know what was going to happen. There was a pause, and then he got up, and I have never relaxed so much in my entire life.
"I actually see it as kind of a defeat. You're supposed to keep them in the room and use your skills.
"Heckling in the UK - and Scotland particularly - is usually a sport. The crowd wants the comedian to win. In Canada, they want to shut you down."
It isn't the first hairy moment Hastings has had during his seven year career.
"I have had a gun pulled on me...that might be the most creative heckle I've had," he said.
"I was in Nova Scotia on my first ever Canadian tour. It was quite frightening.
"That never happens in the UK. At worst you see a knife. But who doesn't have a knife? So you know, it's fine..."
'Not in my club'
Some Fringe venues have a no heckling policy. Tommy Sheppard is the owner of The Stand comedy club.
"There's two types of heckling," he said. "There's one where the performer might get into a bit of banter with the audience, and that can be quite funny.
"But there's also hecklers who are there with the blatant intention of disrupting the show.
"We make them well aware that there are many other clubs and venues throughout the world where they can go and heckle to their heart's content. They just can't do it at The Stand."
But not every comedian minds a bit of heckling.
Meet Gigatron 5000. She holds the official title of World's Second Funniest Computer. She can read the audience, tell jokes - and specialises in heckle put downs.
Her favourite heckle put down is "I'm going to go back in time and kill your parents".
She was invented by computational comic Owen Niblock.
"She has a database of jokes stored as text strings," he said.
"We get a lot of computer-based heckles. You've got very little ram...things about having sex with different types of computers.
"One of the most disruptive heckles I've ever had would probably be a good one for her because she wouldn't know how to deal with it. It was just a high pitched whistle for a very long period of time.
"I made some pathetic joke about having tinnitus. But she wouldn't know what it was, because she won't have heard it before."
A high quality heckle can be one of the most memorable parts of a show.
At a show last week, Marcus Brigstocke was telling a story about Switzerland when an audience member shouted out, "The flag is a big plus".
At another gig, comedy judge Alice Jones heard what she called "the world's nicest heckle".
The comedian was berating the audience for laughing too quietly. A woman put up her hand and said politely, "We think you're very funny. Please just carry on."
Kate Copstick, comedy reviewer for the Scotsman says the Fringe has some of the smartest audiences around.
"I went to see a show called Festival of the Spoken Nerd. They get very high quality heckling.
"It's lovely when you get a good heckle, a smart heckle, and it is marvellous when the comic can bat back.
"But comics need to be very careful. There's this kind of unwritten rule that you have to start off your set with a bit of banter. No, you don't. If you can't do banter well, don't do banter."
But the award for most creative heckle at this year's Fringe has to go to the man who interrupted a show by Australian comedian Bec Hill.
"I asked in my show if anyone has a back up plan for what they would do if anyone tried to mug them," she said.
"A man at the back stood up and I could just see a silhouette. He said, "I'd propose".
"I thought oh my gosh, it's a weirdo from Twitter, he's going to storm the stage.
"As he walked towards the stage he came out of the shadows and I realised it was my boyfriend.
"He got down on one knee and asked me to marry him, and I nodded through sobs.
"Then he hugged me and said, "You have to finish the show now.
"I think if I can come back from that heckle, I can get through most heckles."