Once we (Laura, Liz and me) made this cake that wanted whipped egg whites in it to hold it up. Only, the recipe didn't say at the start "the main thing giving the texture of this cake is whipped egg white", it just had a list of steps. So not realising how critically important it was, I gave the egg yolks to Laura to whip by the time honoured method of putting fork and jug in her hand and saying "X's testicles*" whenever she stopped. (This was before I got my mixer.) It was not actually as flat as one might have expected...

*where X is somebody heartily disliked by her and many others