These creatures you call mice, you see, they are not quite as they appear. They are merely the protrusion into our dimension of vastly hyperintellige… - Douglas Adams

Was there a reason behind it? There would be no point in asking Zaphod, he never appeared to have a reason for anything he did at all: he had turned unfathomability into an art form. He attacked everything in life with a mixture of extraordinary genius and naive incompetence and it was often difficult to tell which was which.

"Sir Isaac Newton, renowned inventor of the milled-edge coin and the catflap!" "The what?" said Richard.
"The catflap! A device of the utmost cunning, perspicuity and invention. It is a door within a door, you see, a ..."
"Yes," said Richard, "there was also the small matter of gravity."
"Gravity," said Dirk with a slightly dismissive shrug, "yes, there was that as well, I suppose. Though that, of course, was merely a discovery. It was there to be discovered." …
"You see?" he said dropping his cigarette butt, "They even keep it on at weekends. Someone was bound to notice sooner or later. But the catflap … ah, there is a very different matter. Invention, pure creative invention. It is a door within a door, you see."
"Is this when you're wearing the helmet?" "Especially when I'm wearing the helmet!"

He inched his way up the corridor as if he would rather be yarding his way down it, which was true.