About 450 children dressed in pyjamas with teddy bears (and parents) in tow enjoyed having the run of the museum on Saturday night.
This year the popular annual event was organised to coincide with the opening of the "Sea Monsters: Prehistoric Ocean Predators" exhibition, which showcases sea creatures from millions of years ago.
Otago Museum weekend supervisor Steven Hird entertained children dressed as King Neptune in a costume he made from scratch, which included a green flowing beard, crown and trident.
Otago Museum social media co-ordinator Max Levitt-Campbell said every gallery was open with all sorts of activities to challenge and excite the mind.
Children were able to take part in games and treasure hunts and win prizes for uncovering educational clues, Mr Levitt-Campbell said.
The number of participants was reduced from the about 600 who had taken part in previous years, and using the whole museum allowed for Covid-19 social distancing, plus proof of vaccination or verified medical exemption using the My Vaccine Pass was required on entry.
The "Sea Monsters: Prehistoric Ocean Predators" exhibition, which features real fossils and life-sized casts of prehistoric creatures up to 13m long, runs until May 1.
