In laboratory experiments of PD, the experimenter has the absolute power to decree the available choices and their "outcomes". (I use the scare quotes in reference to the fact that these outcomes are not to be measured in money or time in jail, but in "utilons" that already include the value to each party of the other's "outcome" -- a concept I think problematic but not what I want to talk about here. The outcomes are also imaginary, although (un)reality TV shows have scope to create such games with real and substantial payoffs.)

In the real world, a general class of moves that laboratory experiments deliberately strive to eliminate is moves that change the game. It is well-known that those who lead lives of crime, being faced with the PD every time the police pull them in on suspicion, exact large penalties on defectors. (To which the authorities respond with witness protection programmes, which the criminals try to penetrate, and so on.) In other words, the solution observed in practice is to destroy the PD.

 1: C 1:  D
2: C (3, 3) (-20, 0)
2: D (0,-20) (-20,-20)

While the PD, one-off or iterated, is an entertaining philosophical study, an analysis that ignores game-changing moves surely limits its practical interest.