No. Sadly, though, it happens all the time. People have assumed that I'm gay because I have long hair, wear pink on a regular basis, and often wear speedos at the beach. These people get surprised when I tell them that I have a steady girlfriend.
It's best not to judge based on appearance. Sometimes they turn out to be the opposite of how they look (or what stereotype you could attach to their looks). A punk who has tons of tattoos, wears a mohawk, and goes commando might turn out to be very polite and classy, while a suit-clad businessman with slicked hair might be trashy as hell. That skinny blonde girl who wears a miniskirt and a halter top could very well be shy, while that heavy brunette girl who wears long pants and a sweater could be an attention whore. The woman who has a buzz cut and wears biker jackets could be straight, and the woman who has long hair and wears dresses could be a lesbian. That muscular football player in the letterman jacket could be the nicest guy, while that scrawny nerd with the square glasses could turn out to be a bully. You never know what someone's going to be like by appearances alone.
Lookism is pretty bad, and sadly it goes back a long time, especially in terms of beautiful vs. ugly. Take the ancient Greeks, for example. The young, beautiful Phryne was accused of blasphemy (a serious crime in most pre-modern societies) and was acquitted because of her looks. The old, ugly Socrates, on the other hand, was accused of a less serious crime and got convicted. Don't forget all the fairy tales and folktales where the heroes are gorgeous and the villains are ugly (although plenty of exceptions do exist). We imagine angels as androgynous pretty boys with curly blond hair and white robes and wings, while we imagine demons as ugly, deformed monsters that look more like animals than people. And speaking of animals, we even subject animals to lookism - if baby seals looked like tarantulas, there wouldn't be nearly as much outrage over killing them. TL;DR lookism is ingrained in human culture. You'd think we'd have moved on from this, but to some extent we haven't. I've even heard studies say that ugly criminals are more likely to be convicted than attractive ones and tend to receive longer prison sentences. And that's just the tip of the iceberg.