It doesn't get much dumber than this...
“Love you too!”

(Talking to boss on phone)
Boss: okay, nice job on that case. Talk to you later.
Me: okay, love you too! (Source)
“I’ve seen better…”

Girl who notices me watching her dancing at the bar: “Do you like what you see?!?”
Me trying to downplay just how much I liked it: “I’ve seen better.” (Source)
“I hope the baby isn’t mine!”

“OH GOD! I hope the baby isn’t mine” (I’m female, I had just found out that my ex had a child…) (Source)
The Tubernonster

I was on hold with my doctor’s office, and during the hold, it was all these advertisements for their new birthing suites, prenatal center, and babypaloozawhatevers. I was on hold for about three minutes listening to this on repeat and then all of a sudden the receptionist picks up with “NAME AND DATE OF BIRTH, Please.”
“My name is tubernonster lastname and um… I’m not pregnant. Did I call the wrong number?”
“This is [name of place].”
“That’s where I meant to call. I need to set up an appointment.”
“Okay tubernonster, can I get your date of birth?”
“Um… I’m not expecting.”
(I can tell by the way she spoke the next questions that she didn’t think English was my native language, and in retrospect I don’t blame her.)
“Your birthday. The day you were born.”
“Oh sh_t. I’m sorry. 12/XX/87.”
IN MY DEFENSE… I had mono and I was really, REALLY f_cking tired. (Source)
Who’s adopted?

I am half Hispanic, half white, but could pass for black. I was adopted by a German/Irish mother and a Russian Jewish father (read: extremely white people).
One day as a teenager I absentmindedly asked my mother “Did you and dad ever think about not telling me I was adopted?” The look of sheer disappointment followed by obnoxious laughter told me everything I needed to know. (Source)
“It’s okay. He’s fine.”

One morning, after another sleepless night (I had episodes of insomnia when I was in my young twenties) , I went to work by train.
There were sliding doors between the cars and exits. The door in my car was actually open. So I slid it shut, then walked headfirst into it. Hurt like hell. Took me a while to fully grasp the scope of my stupidity.
Other passengers were, understandably, perplexed and looked at me like there was something really wrong and dangerous about me.
I said: “It’s okay. He’s fine.” (Source)
Pretty please, officer

“Can you let me go this time? I just got a ticket last week for speeding on this same road.” (Source)
“It tells you what time it is!”

After realizing that the clock app icon on the iPhone was actually keeping correct time after an update: “The clock tells you what time it is!” (Source)
“Are they both the same kind?”

A guy got in the elevator pushing a double stroller. In one half of the stroller was the tiniest little newborn baby I’ve ever seen in my life. The other half was covered with a baby blanket. I wondered if he had newborn twins, or if he had one newborn and one toddler. Unfortunately, what came out of my mouth was “Are they both the same kind?” (Source)
“We will live in a future where people are judged on the…”

As a freshman in high school, I was selected to give a speech to the local Rotary Club on “my vision of the future.” Really big event to a 14 year old, there were 100 or so people and a fancy dinner.
Anyway, I got nervous during my speech, got distracted looking at my note cards and blurted out “we will live in a future where people are judged on the color of their skin and not the content of their character.” (Source)
“I was never good at trash talking…”

I played high school hockey and after beating one of our rivals I was so full of adrenaline that while going into our locker room which was right next to the other team’s, I yelled, “WE JUST SUCKED YOUR DICKS!” I was never good at trash talking. (Source)
The international student

At the store I work at, we require a government-issued photo ID for returns. This is in a college town, so a lot of customers are international students and use passports. A customer came in with a return and used his passport from Korea. I asked him if it was North or South and it took me at least 20 seconds to realize why he was staring at me like I was an absolute idiot. (Source)
“I meant the presents…”

I was in Lush (soap store) getting Christmas presents for my two sisters.
Shop attendant: So, who are the gifts for?
Me: My Sisters.
Shop attendant: OK, what size?
Me: Hmm…thinks for a moment… They’re about 5ft2 and 5ft4.
Shop attendant: I meant the presents. (Source)
“We’re almost done…”

In a middle of an exam the teacher caught me comparing answers with my friend ” You two, stop that right now!” said the teacher, and what came out of my mouth was “wait just a second, we’re almost done” (Source)
“They towed my car…”

Pulled into parking lot – “Holy f_ck I think they towed my car.”
… I was driving my car. (Source)
What a gem…

“What if yelling at a vagina was pleasurable?” We were talking about sound and vibrations and that gem popped into my head. (Source)