If you ask Rick Astley for his copy of the movie Up, he cannot give it to you.
However in doing so, he is letting you down, thus creating the Astley Paradox
A man was in a long line at his local Tesco store. As he got to the check-out, he realised he had forgotten to get condoms, so he asked the checkout girl if she could have some brought up to the register.
She asked, "What size condoms?"
The customer replied that he didn't know. She asked him to drop his pants. He did. She reached over the counter, grabbed hold of him and called over the intercom,
"One box of large condoms, Checkout 5."
The next man in line thought this was interesting, and was up for a cheap thrill. When he got up to the check-out, he told the girl that he too had forgotten to get condoms, and asked if she could have some brought to the check-out for him. She asked him what size, and he stated that he didn't know. She asked him to drop his pants. He did. She gave him a quick feel, picked up the intercom and said,
"One box of medium-sized condoms, Checkout 5."
A few customers back was this teenage boy. He thought what he had seen was way too cool. He had never had any type of sexual contact with a live female, so he thought this was his chance. When he got to the check-out, he told the girl he needed some condoms. She asked him what size, and he said he didn't know. She asked him to drop his pants and he did. She reached over the counter, gave him a quick squeeze, then picked up the intercom and said...
"Mop and bucket to Checkout 5".