1. The show was originally going to be called Get Me Out of Here – I'm a Celebrity! but it was later decided it would work better the other way around.
2. Each season producers meet anywhere between 60 and 90 potential celebrities.
3. Every celebrity thinking about signing up to the show is sent a pack that fully informs them exactly what they're letting themselves in for. No holds barred.
4. Executives also give them the "Talk of Doom", a very frank chat about what's in store.
5. The celebrities are only allowed a few personal items in the camp with them, including three sets of underwear and three sets of swimwear – everything else is provided.
6. The only other thing they are allowed to bring is one luxury item, but this mustn't be anything to stop them interacting with their campmates. So music players, phones, reading material, and iPads are out.
7. The most popular luxury items chosen include photographs, pillows and chairs.
8. Producers originally argued about the underwear allowance – co-creator Natalka Znak wanted them to only bring one pair in, the ones they turned up wearing. But they eventually settled on three.
9. She also almost banned toilet roll, which would have meant the celebs had to use leaves. Luckily for them, this didn't get the go-ahead.
10. One thing that was banned in series 1 was deodorant, in an attempt to make the whole scenario authentic. But the camera crew complained so much about how badly the celebs stank that it was allowed from series 2 onwards. Lol.
11. The show is live. But now there is a deliberate five-second delay in place, introduced after John Lydon decided to say an expletive in series 3 in 2004.
12. The camp is based in a place called Dungay Creek, Australia. It is on the border between New South Wales and Queensland, about an hour inland from the coast.
13. The nearest city is Brisbane, about an hour and a half drive away. Brisbane is where most of the stars fly into.
14. All family and friends are put up in the Palazzo Versace Hotel in Surfers Paradise.
15. The first series was actually filmed in a place called Mission Beach, near Cairns in Queensland, when it was on a smaller scale, but it's been at Dungay Creek ever since.
16. When the show first started, presenters Ant and Dec were put in a massive posh mansion where they had a cook, a cleaner, and other luxuries. But they didn't want to be apart from the team so they asked to be put in the hotel with everyone else.
17. Most years producers have a standby list of celebrities who are either in Australia or ready to get on a plane at any second. But only until the vote-offs begin.
18. The celebrities don't get to speak to their agents once they're out there. They get one phone call at the hotel before they go in, but that's it.
19. To film the show, over 50 cameras are used, 24/7. The footage is then cut down to approximately 30 minutes for each daily one-hour show.
20. There are also 13 edit suites running around the clock.
21. A group of Australians spend three days pretending to be the celebrities the week before the show goes live to make sure everything is working correctly. They do the trials and eat the same food like it's the real thing.
22. The rain you see is real – although they do have a canopy over the camp, about 50 feet high, to stop it getting rained on directly so it doesn't put the fire out. But that's it.
23. There are no clocks in the camp. It's so that the celebrities have no idea what the time is so they are "completely detached from the world." Ant and Dec even wear covers over their watches so they can't get any sneaky looks.
24. Everything the celebrities need to wash themselves with is included in the shower, including shampoo. Although it all has to be biodegradable due to the environment.
25. The celebrities have what is called a "modesty smock", which is a sheet designed to put their head through so they can get changed in front of the cameras without revealing all. It was introduced after the celebs in series 1 furiously complained.
26. When the art department were excavating the first site, they thought they'd found human bones and that the whole production would have to be closed down. It turned out it was actually a load of ostrich bones from a local farmer.
27. In the first series producers forgot about the need for some campmates to have cigarettes. So Tara Palmer-Tomkinson kept on sneaking out to hassle the camera crew for smokes.
28. There's a fleet of vans, called Troopies, that take all crew members wherever they need to be on site.
29. There was an American version of the show for one series. But it rained a lot and was pretty miserable. It wasn't recommissioned until six years later.
30. But there is a successful German version, called Ich Bin Ein Star – Holt Mich Hier Raus! It airs in January each year.
31. The German show is much tougher on the celebs during the Eating Trials. They are forced to eat and drink twice as much as what we see on the British version.
32. Medic Bob initially became a star on the show when Nigel Benn's hand was bitten by a python in 2002. Bob had to come on camera to check him over and from then on he was asked to appear more often.
33. Medic Bob is a huge favourite on the German show as well. So much so that he's even had a single out in Germany based on the stuff he's said on screen.
34. France, India, Sweden, and Hungary have also made their own versions.
35. There is a full security team on duty to stop people getting into the site and also to protect the stars from deadly snakes and spiders. They wear full jungle camouflage gear.
36. Snake Rock got its name simply because when producers were checking over the site there was a snake asleep on a rock. Genius.
37. The show now has an actual bug-breeding factory. Yes, really. The show needs thousands of bugs over the three-week run. As an example, in 2013 a bug breeder bred 250,000 cockroaches, 153,000 crickets, 2.5 million mealworms, 400 spiders, 500 rats, 30 snakes, six 1-metre-long crocodiles, and 20 small crocodiles.
38. Some more stats: In 2004, when East 17 singer Brian Harvey took part in a trial called "House of Pies", 1.5 million flies were used. But because they'd been bred in certain conditions, they didn't actually know how to fly.
39. The crew get through a lot of food each year. For example, in series 13 they got through 15kg bacon, 540 eggs, 7kg muesli, 70kg potatoes, 80kg beef, 60kg chicken, 50kg pork, 20kg fish, 3kg ham, 2kg salami, and 4kg burger patties.
40. The art team start creating all of the props and trials in August, ahead of the November launch date.
41. It isn't an easy job linking the campsite to the production section. It involves four miles of rope, five miles of steel cabling, 60 tonnes of scaffolding, and half a mile of suspension bridges.
42. Ant and Dec work from 2:30am to 10:30am Australian time to make it work for the UK audience.
43. Ant's birthday is on 18 November, which means he's been in Australia over his birthday every year since 2004.
44. There have been a few bug crises over the years. One year execs had a shortage of spiders, so locals had to collect them and were paid $5 a spider. In 2012 there was a cockroach crisis, with hardly any being bred across the country due to the weather. And in 2013 they couldn't include any witchetty grubs on the show because the environment was wrong for breeding them.
45. In 2013 producers ran out of Bushtucker Food because the celebs were so good at the trials and won so many stars. So they had to do an emergency run to their suppliers.
46. A few years ago there was a debate between the art department and the unit (the team who manage the site) over who should look after the dunny (toilet), as obviously no one wanted to. Eventually it was regarded as an "off-screen" item, so the unit crew had to take care of it.
All facts come from the official ITV book I'm A Celebrity... Get Me Out Of Here! The Inside Story by Mark Busk-Cowley.