Is it normal sometimes a sense of childish mischief takes over?
Sometimes no matter how hard I try to contain myself I just end up saying things because I think they are really funny. I went with a friend down to a men's clinic because he wanted to get a HIV test and he was worried. So I drove him down there and I struggled with myself not to say what I wanted to say but when we got there I just blurted it out: "Don't worry so much, Stay POSITIVE".
I know it is terrible but when I get something like that in my mind I just have to say it. Once I went for a regular doctor check up with a girlfriend and I came out and said "Yeah I am better than I expected, he gave me six months to live" then laughed at her shocked face. I can't even say why I say these sort of things and the worst part I still laugh about it to this day.