Motorists traveling on Auckland could have been thinking for someone who was pulling the wool over their eyes.
But as Ellerslie resident Ada Rangiwai got closer, she was shocked to see there really was a truck on the city's southern motorway.
"We saw the sheep on top of the roof and I'm like 'Oh my god, I have to record this, this is gold'."
Rangiwai said she just saw the Takinini turn off at around 5pm on Sunday.
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The driver was pulling over on the side of the motorway as Rangiwai was traveling in approach.
She said she had someone who knows the truck driver.
In the video, the truck is pulled over with its hazard lights on the back of the truck.
A man can be seen walking around the truck, looking up towards it.
Rangiwai said the order was funny to watch and was not something you see every day.
"I do not understand how the sheep got on the roof," she said.
"There must have been a hole in the roof and it's climbed on its mates."
Rangiwai said the sheep did not seem nervous and it was just standing there, unfazed by the attention.
"It was surfing," she said.
The truck was owned by Heikell Transport, which specializes in livestock transportation throughout New Zealand, according to its website.
Heikell Transport said it would rather not comment.
New Zealand Transport Agency spokesman Darryl Walker said he had seen the video but said the incident had not caused any traffic problems on the motorway.