1、怎么是你？ When you encounter someone you're unexpected to see, you can say "怎么是你?" to show your surprise, or just implying a question "Why you are here ?". Anyway, this is an unfriendly sentence, showing the speaker's unwelcome attitude to that person. 2、怎么老是你？ “老” in this sentence means "again", emphasizing the speaker's disgust emotions. In sum, all these sentence are very rude and unfriendly, I guess that's why the Chinese people have never said them to you.

It's a joke. the chi-english way to translation怎么是你and怎么老是你is how are u,and how old are u respectively.It's the same as 好好学习，天天向上is translated into “good good study, day day up". The true meaning of 怎么是你 is to express a surprise.it's "I can't believe it is you..."and 怎么老是你 is to express impatience."why it's u over and over again."

怎么老是你的意思：有点对那人产生一种厌恶，表示厌恶的。怎么是你的意思：表示惊讶的

老：1、年龄大（pinyin: nian ling da ) old 2、总是（pinyin:zong shi) always

怎么老是你--有种厌烦的情绪， 怎么是你---表现出说话者很惊讶