When I first interviewed you at Harvest festival in Sydney in 2011, you showed me a photo on your phone of decapitated human heads in a large freezer. The freezer belonged to a guy you sourced bones from, which you used to distribute new music. This is more of a comment than a question.

Gosh, that’s a great memory. Wow. I remember having that picture – and I would show it to people. Not to very many people but to some people.

I don’t know if you believed it at the time but, yeah, it’s real. It’s people who have donated their bodies to science, and then they use all the other bits. And this guy I know who works at the skeleton place [Skulls Unlimited in Oklahoma], he gets the heads and then turns them into skulls [using flesh-eating bacteria]. But they come in as just heads! It’s the most bizarre thing I’ve ever seen.

I happened to be at his place on the day that the frozen severed heads came in. He showed them to me, and he knew I took a picture, but he was like, “Don’t let that out. You can show it to people on your phone, but don’t ever put [the photo] anywhere.” So it’s our secret. Me and you.

Me, you, and the Guardian readership. What has been the most memorable interaction you’ve ever had with a fan?

A lot of times we’re meeting people – and I think it’s just the nature of the type of music that we do – who are willing to tell us about really tragic, sad things in their life. I don’t take it lightly. You’re talking to someone and they’re gonna reveal that their mother has died, or their brother is dying of cancer or something – it’s never anything too sexy.

Who’s the most famous person in your phone?

Chris Martin and Miley Cyrus? Are they famous enough?

What’s the latest book you read that you loved?

My favourite books really are the same books they’ve been since I was a child, like, Dr Seuss books. And now I get to read them to my kids. The Grinch that Stole Christmas, or The Cat in the Hat. I feel very justified: I’ve liked them for my whole life, and now I get to read them to my little boy.

If you could change the size of any animal to keep it as a pet, what would it be?

My little boy’s name is Bloom and he’s fallen in love with crocodiles. He wants to get one for Christmas. He thinks Santa Claus is going to bring him one. I just wish that they didn’t grow up to be these things that will bite your face off. But he’ll learn that eventually.

Maybe we should get him a little baby one, and when it gets big we’ll give it to someone else. I told him, ‘Well, we could tape his mouth shut, and you could probably sleep with it.’

Your live shows are famously rapturous, but there’s always a lot going on. What’s the most chaotic thing that’s ever happened to you on stage?

We don’t do fire but we did do fireworks here and there. We were playing a series of shows in Texas and bought a bunch of fireworks and, while we were playing, we literally shot them off the stage. They’re shooting up and hitting us, they’re hitting the audience, they’re hitting the ceiling, they’re hitting everywhere. I mean, it was just fucking insane – you could shoot someone’s eye out, you could shoot your own eye out, you could catch the place on fire, we all could have died. Luckily, none of that happened and we came to our senses, and we really only did it a couple of times.

We actually tried to do the fireworks [once] when we weren’t playing to an audience, just to be like, “How would we do this?” And we couldn’t do it because it’s too scary. But in front of an audience, adrenaline kind of gives you superhuman strength.

No. No one should ever do that. But we did it. We got away with it. And we will never do it again. On purpose.

Have you ever had a cringeworthy run-in with a celebrity?

All the time. Really. The first time we met Paul McCartney – he wasn’t there to meet us, he was at one of these festivals, and he came in through the backstage. No one really knew he was there. He came in with his wife, Linda, and I just followed him up on stage. He thought I was part of his entourage – apparently he didn’t mind that I was there.

But I stood right behind him as he watched Neil Young play. I’d seen Neil Young play – I was there to look at Paul McCartney more than anything else. It was a long time ago – 1993 or something like that – but I remember: his ear was very crusty. I mean, you’re just looking at Paul McCartney as a human, you know? You don’t get to do that very often. And I remember looking at his ear and – look, sometimes when you’re travelling around a lot, your ears are kind of crusty.

I don’t smoke pot, and he had a big joint, and he handed it to me as if I was part of his entourage, and I took a big puff of it, which I shouldn’t have done, but I thought, “Well, how often do you get to smoke a joint with Paul McCartney?” It was amazing.

Do you have a nemesis?

To tell you the truth, it’s you right now. Talking to you makes me realise I don’t have any answers. Except that I took a picture of some severed heads. You and I, that’s all that we know.

Do you have any party tricks?

I did have one. A magician guy showed me this trick where it looks like you could put a big nail through your arm. You use this glue, and you can [stick] this nail into this hole that you made in it, but no one knows that you have the glue on your arm. I would carry around a little bit of fake blood, and I’d put this nail through my arm – and it looked very convincing. I would tell people, like, “I don’t have any feeling in my wrist right here – I can actually put a nail through it! I’ll show you, it’s cool.” And people would be like, “Fuck! That’s fucked up!”

On what sorts of occasions are you doing this? Like, dinner parties or … ?

When you tour around – especially like in the late 80s, early 90s – you just end up having to meet a lot of people and do a lot of things where you can feel really out of place. So you would want to have a thing that you can do. Like, hey, I don’t know what to talk about – but if I do something like this, it could break down a barrier between me and the other weirdos.

You want to have something to offer … like when I showed you the severed heads! I mean, that was a party trick of sorts.

Do you believe in ghosts?

After my father died, the idea that you could visit people in your dreams – if I thought about it that way, I could think, “That’s really him speaking to me”, you know? He died of cancer, and he was old; it was horrible. But I could see that if I was younger, and it was something a lot more painful – a lot more tragic – you could believe anything that gets you through a moment like that.

When my wife’s father died, we were away, and she didn’t ever get to see him again. She goes to seances and stuff now, she wants to visit him – and when things happen, and she says, “I think that was him!” I say, “Yeah! If you feel like it’s him, then it’s him!” I believe anything – if it makes you happy and it makes you believe that the world is a great place then, yeah, sure!

• The Flaming Lips’ Australian tour kicks off in Adelaide on 30 January before dates in Melbourne, Sydney and Brisbane