Paris Hilton's Chihuahua Tinkerbell is an impostor, it has been claimed.The hotel heiress's favourite pet - who she was once inseparable from - disappeared in 2004 and has rarely been seen since.Paris recently brought a Chihuahua to the set of her new film 'The Hottie and the Nottie' which she introduced as Tinkerbell but when compared to old photos of her mutt it doesn't appear to be the same dog.A representative for Paris has denied the canine switch, saying: "There's only one Tinkerbell. The colour of Chihuahuas change as they grow older."But pet expert Charlotte Reed, author of 'The Miss Fido Manners Complete Book of Dog Etiquette', told Us Weekly magazine: "A Chihuahua's fur may grey with age, but dog nail colour stays the same. "In the older picture, Tinkerbell has a black nail, while in the new one, the nail is white. I don't think it's the same dog."