Popular culture was also reflected in the most common pet names, with Twilight saga heroine Bella in the top two for cats and dog names.
Films like Marley and Me, Milo and Otis, and The Lion King were also a source of inspiration, with Simba a popular name among cat owners.
And while Katniss from The Hunger Games did not make it to the top 20, Ellenco said there was one on its books.
Wellington dog owner Phil Hope, whose wife chose the name Bella for their 9-year-old Hungarian vizsla, said he was not surprised at the popularity of the name.
Mr Hope said he knew a couple of parents who had chosen the name Bella for their children lately.
According to Internal Affairs, Isabella was the sixth most popular girls' name last year, while the diminutive Bella was the 34th most popular.
The name means "beautiful" in Italian, and Mr Hope reckons his Bella fits the bill: "She looks lovely."
Rob Ellis, the owner of Auckland pet hotel Pets in the City, said there were about 20 cats called Oscar on his books and a "ridiculous" number of dogs called Bella, with almost 90 canines sharing the name.
"When reception calls for Bella to go home, every night the call back is, 'Which Bella? Bella who?' Because there's so bloody many of them."
As for royal baby name candidates, Mr Ellis there were 21 dogs called George on the books and a handful of cats and dogs called James.
New Zealand Kennel Club president Owen Dance said a lot of people saw their dogs as children, and his own dogs had people's names.
TOP DOGS' NAMES
1. Bella
2. Molly
3. Charlie
4. Max
5. Oscar
6. Poppy
7. Ruby
8. Coco
9. Toby
10. Jack
(Source: Pet insurer Ellenco)
TOP CATS' NAMES
1. Oscar
2. Bella
3. Molly
4. Charlie
5. Max
6. Coco
7. Monty
8. Milo
9. Poppy
10. Chloe
(Source: Pet insurer Ellenco)
TOP GIRLS' NAMES
1. Olivia
2. Sophie
3. Emily
4. Charlotte
5. Ruby
6. Isabella
7. Ella
8. Amelia
9. Sophia
10. Ava
(Source: Department of Internal Affairs figures for 2012)
TOP BOYS' NAMES
1. Jack
2. Oliver
3. William
4. Liam
5. Mason
6. Samuel
7. Jacob
8. Lucas
9. Ethan
10. Noah
(Source: Department of Internal Affairs figures for 2012)