It was a double take for Stephen Evans as he watched a clutch of lizard eggs hatching. He assumed he was about to become the proud owner of twins when two little heads popped out of one egg.

Then he realised he had witnessed the birth of a rare two-headed bearded dragon lizard -- believed to be one of just four in the world.

Evans, 34 from Birkenhead near Liverpool, has bred bearded dragon lizards as a hobby for 17 years, and this is his first "double header".

Evans' children have named the dragon lizard Olaf after the snowman character in the Disney epic Frozen, though the lizard spent Friday in a temperature controlled incubator, enjoying life unperturbed by having two heads.

The clutch of eggs in the incubator were checked by Evans Wednesday evening when he realised there were two heads in the shell. When he checked again Thursday he was shocked to discover the two-headed lizard, just a few centimeters in length.

He told local media: "I couldn't believe it when I noticed the two heads shared the same body. I think everyone is shocked."

Evans and his wife Jodie keep nearly 50 bearded dragons and specialise in breeding lizards with rare colors and unusual patterns, known as "morphs".

Evans commented: "I think there's only ever been three or four cases of bearded dragons being born with two heads. It's certainly not common and I don't think any of the other babies born from the clutch of eggs will be born with two heads."

"Other than the fact it has two heads it seems to be healthy and strong -- it hatched on its own and that is a good sign. The two heads move independently and it does move about normally," said Evans.

Olaf's sex will be unknown for another six to seven weeks, but for now the dragon lizard seems healthy, though the new arrival will be given special care and attention until Evans and his wife are confident the new arrival is doing well.

Meanwhile the two heads are happily munching their way through a diet of crickets, mealworms and salad.