Cowboy hats were a popular choice for dressed-up students at the annual Hyde St party in North Dunedin.
Residents of the street's flats and nearly 4000 ticket holders were ready to party at the sold-out event today.
Students were also dressed up as pirates, sailors, fairies and medical staff.
Characters range from Minions to animals and at least one person was dressed up to be several decades older than somebody requiring identification to purchase alcohol.
Free food and water is also on offer.
Mr Robertson said it was the first Hyde St party since he had been appointed to the role, and described it as "organised chaos".
The party was once a notorious event, but harm minimisation has been a feature since the roof of a flat collapsed in 2012.
It then became a ticketed event organised by the Otago University Students' Association.
"I think this is a really good example of the fact that we can help create an event that's still fun, but has got a lot of safety built in around it," Mr Robertson said.
OUSA president Liam White opted for a mix of Crocodile Dundee and Australia Zoo for his outfit theme, complete with cowboy hat.
He hoped everyone would have a fun time while staying safe.
As of 6.45pm, no arrests were made, a police spokesman said.
