A sarcastic statement mocking the type of netspeak that is popular among 12-17 year olds. When spoken in word, it is spoken in a serious (thus ironic) voice while pronouncing the "xd" as "ex dee".
You're wearing a Hot Topic Invader Zim shirt, huh? Well would you look at that, he's riding a moose and Gir is eating a taco. Lol so random xd.