I've run into too many situations where I said, "I fangirled" and people look at me like I said a dirty word or swore at them. And then I have to explain it. So here's how I do it:

To Harry Potter fans: It's like being told J.K Rowling wrote a book for you and Harry Potter is real.

To Twilight fans: It's like Edward saying he loves you.

To internet users: It's like your meme becoming insanely popular.

To animal lovers: It's like being able to speak with animals.

To food lovers: It's like being able to eat all you want and not get fat.

To coffee lovers: It's like you have free coffee at Starbucks for life.

To chocolate lovers: It's like you have an endless supply of chocolate.

To tea lovers: Do you want a cup of tea?

To movie fans: It's like the guy getting the girl, except you're the girl/guy.

To book lovers: It's like your favourite book having a sequel that's out ... NOW!

To Glee lovers: It's like being told that you're in the Glee club.

To Star Treks lovers: It's like another movie coming out ... that'll be better than all the others combined.

To Star War fans: It's like Darth Vadar going, "jokes" after he tells you that he's your father.

To iPhone lovers: It's like there won't be another iPhone after you buy this one for at least a year.

And that's all I can think of for now ....