With US still over 1 year away from being able to launch humans into space again, what a story it would be if someone stowed away in a cargo mission. It would be like a Doolittle raid, but a raid against bureaucracy & management. It would be riskier than Alan Shepard's 1st flight, because the cargo modules have no launch abort capability. Beyond that, it would be the same as that 1st flight, despite all the concern about minutiae in the flight termination system, life support system, & micro meteoroids. Indeed, much of the last 8 years of pain has been micro meteoroid shielding standards.
The stowaway would be a man, of course. He would have a food supply & a bathroom hidden somewhere. Once on the space station, they would have the issue of feeding him, not having enough room in the Soyuzes to evacuate the station, the life support system encountering loads not seen in 8 years.
The real drama would be the consequences of stowing away. Would he be shot for treason? Would NASA give up on human spaceflight entirely because they couldn't enforce enough meaningless regulations? Would private space programs tolerate more risk?