"I love Joan and find her absolutely hilarious. On my first day she was saying these jokes and I'm just laughing and one of the producers was like 'what's he doing? Make him stop.' But Joan loves it, she loves my laugh so it became a thing where they just let me laugh." One imagines that Rivers would be an eccentric boss, but Kotsiopoulos says, "I love her, she's incredible. She's an inspiration. She keeps reminding us how lucky we are, which is wonderful to hear because sometimes you forget.
"Joan told me recently the median age of her fans is 22. I've had established comics tell me they are in awe of her. To be 80-years-old and still be relevant with a young audience is quite remarkable. She is a very lovely lady with a huge heart."
Part of the perverse fun in watching Fashion Police is seeing who the hosts pick for worst-dressed. Then the single worst-dressed of the week is aptly named "Fash-Hole of the week". Do the stars take offence? "Sometimes yes, sometimes no," says Kotsiopoulos.
"Drew Barrymore has been very cool about it. I saw her at an event and she came running up to me and said, 'I love Fashion Police! I love it when you guys rip on me. And you guys were right about that dress, it didn't look good on me.'
"Yes Joan can be super harsh. But if we're talking about you on Fashion Police it means you're relevant in the fame sphere. We're talking about very, very wealthy, very beautiful, very famous - did I mention wealthy? Let's not feel too sorry for them. They're doing just fine."
I ask Kotsiopoulos who his fashion spirit animal is, but he didn't understand so I explained that mine is Edina Monsoon (Jennifer Saunders) from Absolutely Fabulous.
"Ahhh, I love Ab Fab. You know what's great about that show? It holds up. And here is why. You know Joan hates Prada, but I say buy those crazy pieces, the crazier it is the more likely it'll never go out of style. Edina Monsoon wore crazy-ass clothes, she wore fashion which is kind of timeless. Crazy fashion never goes out of style. It's those really key, super-super trendy pieces that go out of style but the crazy Prada shoes with the flames on them - why would you get rid of those? They're brilliant. And you bust them out every so often and people love them. So my fashion spirit animal would be Steve McQueen and Jake from 16 Candles."
Even a fashion authority like Kotsiopoulos suggests it's a mistake to slavishly follow fashion trends. "Accessories are a great way to incorporate trends into your wardrobe but you have to wear what looks good on your body."
Kotsiopoulos has just released his first book, Glamorous by George. "On Fashion Police the biggest compliment we can give a woman is that she looks like a movie star and that means something. It's not about wearing stilettos everyday, it's about having that extra oomph in every aspect of their lives, it's very fashion heavy. It's hair and make up, it's etiquette, maintaining, aging, plastic surgery. It's very accessible, it's not rocket science."
Fashion Police screens on E! Saturdays at 8.30pm.