This from John Godsey, who reports the story that Barth told him about the writing of the Barmen Declaration:
…they appointed three persons to work on a common theological declaration for the meeting. These were Thomas Breit, a Lutheran from Bavaria; Hans Asmussen, a Lutheran from the Old Prussian Union; and Karl Barth, a representative of the Reformed. Breit wrote the other two to meet him at a hotel in Frankfurt, where they could work out the declaration together. This they did, and during the morning they outlined the six points they wanted to make and decided on their plan of action. They would eat lunch at the hotel, then each go to his room and work out his own statement concerning the six areas, beginning at two and ending at five o’clock. Then they would come together at five, compare what each had written, and work out a common statement based on their three contributions.
Lunch arrived, and it was a fairly heavy one, served with wine, and afterward there was coffee and liqueur and big black cigars. Then they went to their separate rooms. Barth ordered more coffee to be sent to his room and set to work, writing the whole declaration as it now stands, Bible quotations and all, between two and five…At five o’clock there was a knock at the door. Asmussen entered and sheepishly explained that he had fallen asleep and slept the whole time. A bit later Breit came and exclaimed, “Oh! Ich habe geschlaffen!” (Oh, I went to sleep!). Both the Germans had lain down for their afternoon nap, a custom in Germany, had overslept, probably because of the wine and liqueur, and came with blank sheets of paper, whereas Barth, not accustomed to the nap, had written the Barmen Declaration! The other two men readily accepted his work, and thus it was that the Swiss Reformed theologian ended up writing the declaration or confession for the most important synod during the Church Struggle. Sometime later Asmussen made a special trip to Bonn to ask Barth if he could make a small addition to point 2, and Barth said, “Sure!” The words, as translated into English, are these: “Through him (Christ) befalls us a joyful deliverance from the godless fetters of this world for a free, grateful service to his creatures.” Barth’s comment on the whole affair was the following: “Church history is probably full of queer incidents like this!”