Blue weighs 92.3kg and has to have his veterinarian visits in the carpark because he is too big to have inside.
Owner Tracey Cookson said the 3-year-old Neapolitan mastiff only weighed 5.6kg when she got him at 7 weeks old, but he had grown a lot on four cups of biscuits a day.
"He probably shouldn’t have got as big as he is, but he has."
Ms Cookson said having a dog as big as Blue was "fun sometimes".
There was no holding him back when out for walks.
"He will pull you for Africa."
"He’s bigger than everything, but everything scares him — fireworks will just about tranquillise him.
"He comes across as big and tough, but that’s about it."
The Neapolitan mastiff mostly spends his time indoors with the family and loves to sleep in the children’s beds.
He is very protective of his own.
Ms Cookson said she got him from Oamaru after seeing a Facebook post.
His previous owners had lost their house and were living with eight puppies in a caravan.
