Rolling On The Floor Like Draco Malfoy
This term refers to the character Draco Malfoy from A Very A Potter Musical, the fan-made parody musical by StarKid Productions. In the musical, Draco is known for rolling around on the floor, so, to ROTFLDM is to roll around in an imitation of Draco.
Person 1: My friend just said she was a Hufflepuff, and I said "What the hell is a Hufflepuff?"
Person 2: ROTFLDM
A Harry Potter role-playing site, Unrelated Wizards was created when a group of people would spam the comment section of photos on the website Unrelated Captions pretending to be characters . They were then yelled at by Unrelated Captions's Admin. The group decided they must form their own website, and elected the one who called himself "Remus Lupin" to do so, which he painstakingly did. The Unrelated Wizards now spend their time having parties on their forum
Quoted from the site:
Founded by a group of rebels who would take over the comments of photos with unrelated captions, Unrelated Wizards is a website. That's all I have to say.