There was once an incident as a kid where I was acting foolish somehow at the dinner table talking with my brother, who maybe didn't care that much anyways as to what I was doing. My grandfather, whose first language is Spanish, then went on to get a bit angry at me and said 'Do not molest your brother!', to which we both couldn't stop laughing at for a few minutes. Anyways, here I am now actually getting alright at my spanish, and I now realize he just took the spanish word for 'to bother/annoy/otherwise disturb' (molestar), and mistakenly used the word for something that was totally inappropriate in english usage (Generally to be 'molested' in english implies something that tends to send people to the psychologist, and to 'molest' someone is something that sends people to jail, at least in modern parlance).
So now, my question is this - Is there any words that sound similar enough between English and Spanish that have different connotations than what I might expect while blurting out, which I should avoid using while speaking Spanish, in case I end up saying something accidentally offensive or hilarious at my own expense? I'm sure a bunch of you here are native speakers that have some amusing stories that we can learn from, let's hear them!