Almost a year ago, my cousin came out to me as asexual aromantic. She told me not to tell anyone, and I was the first person she ever told. Which was a good call, as I happen to be asexual, though romantic, myself. A couple weeks later, my mom and I were chatting and my cousin happened to come up. My mom then said, "She's really not into boys, unlike her half sister was as a teen. Is she asexual aromantic or something?" As neither my brother and I are...well, not your typical 15 year old heterosexual males, she's quite adapt to terms and such in the LGBT community. Anyway, I sat there for a moment, not sure what to say, and then decided to explain it to her, telling her to not tell my cousin's parents as she wasn't out to them yet. My mom said, "Oh," went silent for almost half a minute, and then blurted out, "Our gene pool is going to die."
A couple months ago, my dog was refusing to eat the food my mom made him for dinner, and he hadn't eaten his breakfast either. Our dogs can often be picky eaters. Frustrated, my mom said, "Max, if you don't eat your food, you're going to be one skinny bitch."
Another time was in 2013, on my brother and I's 14th birthday (we're twins), we had done a small celebration thing with our parents, and we were having that damn awkward moment when you've opened all your gifts and you're really not sure what to do. My mom broke the silence by saying, "Well, this is the last time we're going to see our kids this weekend." My brother laughed so hard he almost fell out of his chair on to the ground.
My dad has said some funny things to, but most of them not as good as my mom.
Edit: Typo that took me a long time to notice.