Almost all of the different characters in the story are, in fact, alternate versions of Daniel from another point in time. When Daniel first meets his future self from one day into the future, the future version identifies himself as "Don," ostensibly Daniel's twin brother. The next day, when it becomes Dan's turn to meet a version of himself from yesterday, he adopts the role of Don. (When a third Daniel appears, he is sometimes identified as Don II, or ultra-Don.) The female version of Danny has a similar relationship with alternate versions of herself; she is Diane when she meets a version of herself from the future, but when she plays the role of the future traveler she adopts the name Donna. Diane has an Aunt Jane, who is the elderly version of herself, and the female equivalent of Uncle Jim.