Something of a mystery has erupted in the US over a man, a suspected burglary and a Halloween fancy dress costume.

In a case that could have come straight from Scooby Doo, a man was arrested earlier this month after being found by police outside an Oregon museum wearing some kind of creature from the Black Lagoon outfit, the Daily Mail reports.

The police dog bit him, but Gregory Liascos insists he was just waiting and happened to be wearing the Halloween costume his kids gave him.

Upon closer inspection, a caretaker found a hole had been cut in the wall of the Rice Northwest Museum of Rocks and Minerals and somebody had entered, dropping a trail of moss behind them.

Mr Liascos is now facing burglary and mischief charges, but insists he is innocent.

Given most people's experiences of Scooby Doo, perhaps the police may be wise to check the caretaker - or the man who owns the abandoned fairgroundā€¦