My youngest sister told me this story at the weekend. And I believe her, because this kind of thing happens to my family...
She was working as a carer for (I think) Scope, and they had taken a bus load of their clients out to Portsmouth for the day. She went to the toilets with one of them, and they needed to go into the "disabled" cubicle. Which was in use. So they waited. And waited. And waited.
After several minutes with no sign of life in there, Sis knocked politely on the door. There was a muffled "I'll be out in a minute" from inside, and then a few more moments of silence.
Eventually the door opened and out waddled a bloke in a huge, heavily padded seagull costume. He squeezed past Sis and her companion, nodded politely (beak and all) then left the building.
And when Sis got back to the bus nobody believed that it had happened, and made fun of her because they'd taken so long in the toilet. She said the worst thing was spotting the seagull man in the distance, handing out leaflets but by the time she called anyone else's attention to him, he was out of sight as the bus drove away.