text: The appearance to "the twelve" is not even a particularly challenging apologetic.  Luke 24:33 has "the Eleven and those gathered with them" (τοὺς ἕνδεκα καὶ τοὺς σὺν αὐτοῖς).  Acts 1:22-23 indicates that the person to take Judas' place should be "one of the men who have been with us the whole time the Lord Jesus was living among us, beginning from John’s baptism to the time when Jesus was taken up from us." It's not too difficult a leap to consider that Matthias, as one with them from the beginning, would have been both in the upper room and at the Ascension as testified in the Lucan accounts.  
  Having been written after the Ascension event, Paul is perfectly correct in mention of "the twelve" with reference to Matthias as both one of the (then current) twelve as well as witness to the Jesus' Ascension and the Pentecost event.  WRT the "fun" of Judas as the bad guy; I would suggest it is a warning akin to Paul's in 1 Cor. 9:27 - salvation is ours to grasp, but we may fail to do so.