My cat Max had been abandoned by his previous people, but was also rescued by a mailman, who would share his tuna sandwich lunch with him, giving him the nickname “Tuna.” He brought Tuna to a hospice run by some nuns, who had a feral cat colony on their grounds. The sisters called the TNR rescue group that tended to the colony, to help Tuna, through which we wound up adopting Tuna, now Max. So this story line resonates with me and Max. We KNOW there are mailmen!!
It’s not a pun, but an allusion and a call-back.