The coin tossing, for one. The law of probability stands firmly against that many "heads" in one sitting.
The arrivals and departures of these two are quite ironic as well. They seem to just appear and disappear at will. It is an absurd bit of theatre.
The deaths of R and G are never reported in the play, even though the audience expects this event. This is one of the themes of absurdity and the believeablity of theatre--that people believe what the actors want them to believe. By this idea, we should believe that R and G are still alive and never died even though we know the opposite is true in Hamlet.
The complete slanted inversion of Hamlet (The holiest Holy of all theatrical productions) so that it is told 'through a glass darkly' by a couple of minor characters and that those characters are not 'in' the play but cluelessly bouncing around, (ie at the whim of a fickle, God-like playwright who can mould reality) that is ironic. Hamlet turns from the world's best loved tragedy into a surreal farce.
Yesterday R+G were in the real world, normal R+G, or were they? "What's the last thing you remember", "I forget"... but then they were "sent for" and entered this weird theatrical drama. And their comi-tragic doom is certain. There's always blood. "The blood is compulsory." It is ironic because the characters have become self-aware of their environment enough to observe it is barely real, but not so self aware that they say, "oh we are in a play." The truth keeps slipping away from them, they go in the play, behind the scenes with the actors, back in the play, mind-games and reality puzzles,
"One... probability is a factor which
operates within natural forces.
Two... probability is not
operating as a factor.
Three... we are now held within sub or supernatural forces"
Those supernatural forces are 'the magic of the theatre'.
The most important and ironic situation of R&G are dead is the petty but symbolic confusion that Rosencrantz makes when he introduces himself to the Tragedians. Rosencrantz introduces himself as Guildenstern and then rectifies his mistake.This depicts the insignificance of their identity and it shows how little power they exert upon themselves despite the fact that they are completely free.Another ironic situation that illustrates the above idea is when T.Stoppard make R&G travel through situations. At one moment, thet are on their way to Elsinore and the other instant, they are already in Elsinore.