Like a dog eating mango

All my friends who have dogs always ask me to not give them chocolates. I had a dog when I was a kid and once, I gave him chocolate. It made him felt really sick. That's why he hated till the end of his life. Lesson: chocolates make people happy, not dogs !!!

Well, what chocolates, mango and dogs have in commom ??? Well, it's bad to give chocolates to dogs. But in Brazil, when you say someone looks like a dog eating mango, you mean his/her is really ugly, kind of nature forgot about him/her. Yeah, plastic surgery is waiste of time, money and the doctor's skills.

I've never seen a dog eating mango. Once, I got an e-mail from a friend that has a photoshop work: a dog eating mango. It was really ugly, but I don't know what made it ugly: the dog eating mango or the crappy photoshop work.

So, how do I say a person is really ugly "like a dog eating mango" american way ???