As I step through the front doors of Ripley's Believe It Or Not!, London's only "odditorium", I'm greeted by a woman gingerly fingering a shutter that bears a stark warning – Open At Your Own Risk. She picks at its edge nervously and then, with some encouragement from a friend, opens it suddenly to release a peal of bloodcurdling screams. Not hers. They're coming from the cupboard. She shuts it quickly, slightly embarrassed, and pops a lemon bonbon into her mouth as if to pretend it didn't just happen.

I smile at her. She smiles back awkwardly and I wonder if Ripley's is going to be like this all the way through – a museum filled with slight embarrassments. I've never been to an odditorium before. It's a bit like a Victorian freak show and I'm not quite sure what to expect.

Robert Ripley, an American illustrator, turned to cartooning strange sporting facts and began to develop an obsession for everything weird and wonderful. Before long, he was travelling the world collecting oddities – lambs with six legs, a huge ball of string found in a cow's stomach, or a sculpture of the Beatles made from chewing gum.

I'm greeted in the entrance by a trio of mechanical waxworks. There's Francesco Lentini, a three-legged man playing the banjo. Next to him stands a Padaung woman, her neck trussed up with copper hoops, and inside a bird's cage to their left is the midget Alypius of Alexandria, who stood 17in high. I stare at them. They all have physical deformities. I can't help feeling a little uneasy.

I'm being shown around by a woman called Jessica. She's been here for three years and has worked her way up, having started on the tills. She's lovely and has an easy charm that endears me to her from the off.

"I love it here," she tells me, showing me into the artists' section where she presses a button on the wall. A box in front of me lights up and I peer into it.

"What's that?" I ask.

"It's a portrait of Jimi Hendrix painted on dung," she tells me, happily. "It's done by an artist called Enrique Ramos. He was quite prolific."

She's not fibbing. The lion's share of odder pieces are the work of Ramos. He's done a picture of Marilyn Monroe formed from dead butterflies, a portrait of a slightly cross-eyed Princess Diana made from discarded lint and a tableau of Charles and Diana's wedding in which the royal family are all ants.

"Enrique Ramos had quite a fertile imagination," I opine, staring through a magnifying glass at Prince Edward's head stuck on to the body of an upstanding ant.

There's no doubt about it, Ripley's Believe It Or Not! is packed full of bizarre items such as a bust of Judas made out of toothpicks. In many ways, the fact that someone sat down and decided to make a bust of Judas entirely from toothpicks is an unadulterated joy, but there are also exhibits that feel as if they aren't entirely appropriate for modern sensibilities.

Jessica presses another button and a waxwork of Grace McDaniels, the "mule faced woman" spins around to reveal her hideous and unfortunate facial deformity. I turn to Jessica. "Do you worry," I ask, "that these sort of exhibits are simply inviting people to think of disabilities as entertainment?"

Jessica ponders this for a moment. "I don't think so," she answers. "I like to think they're celebrating these people's achievements. And it is historic. Although, having said that, Grace McDaniels had a terrible life." And then she proudly tells me how Ripley's is fully wheelchair accessible.

Perhaps I'm being oversensitive and Jessica is right – there is a historical element which is acceptable for a museum to explore, but I doubt whether Grace McDaniels would imagine that her miserable life would be celebrated by a waxwork that spins. Anywhere that showcases people who have led a terrible existence simply because of the way they look, is treading a thin line.

That gripe aside, there is much at Ripley's to enjoy and I suspect that children, especially, will love it. Do have a go in the Mirror Maze. Despite being freaked out by the fact I seemed to have a doppeleganger wandering around it at the same time, I made it through in eight minutes, 49 seconds. Beat that!

Oh. And the building is haunted. "Avoid the upper areas," says Jessica, whispering.

So for your entrance fee to Ripley's, you might see a ghost. Believe it. Or not!

• The London Pavilion, I Piccadilly Circus, W1 (020-3238 0022, ripleyslondon.com). Adults £26.95, children £21.95, under-fours free

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