About 4 times a day he would say, " Hey, Ewelina. Pee." After getting the appropriate reaction, ("David!") He would say "Letter, 'P'!!!" This continued for weeks after we stopped responding to it in any way. (We had a strict "no potty words unless you're in the bathroom" policy, and the kids never cared to break it, except for David during this short phase, which was more of a display of his wit than a desire to say a forbidden word.)
Also, when he would get offended, and he has always been very sensitive that way, and he wanted to express his frustration and dissappointment in us, he searched his darling little brain for a word that would cut us to the core. One that would show that he could completely reject our teachings, and be bad, if we pushed him too far.
And he found the perfect one. If we ever implied that he had done something he shouldn't, or tried to correct him etc. he would walk off to his room and turn back just to say, "Alcohol!" in a very defiant tone. Surely alcohol must be such a bad thing that the word alone would shock us horribly.
Sad for him, it never did. It did, however, give us a good laugh and a great story to pass down for generations.