I'll take a shot at this...
Alright, I am looking for two aircraft. They were, as far as I know, the only air-refueling tanker that could fly supersonic. And by "tanker" I am not referring to any of the fast jets that could carry a buddy store, but instead actual aerial refueling tanker planes. The catch is, neither one was designed to routinely fly that fast, in fact, one of these was specifically to be limited to no more than .96 Mach, due to control problems above that. They both had two specific design features in common that were not found on most of their contemporaries of the period.
Name the planes, and for bonus, name the two design features that they shared.