So I found this joke when I was watching a vedio clip of The Ellen Show (https://www.youtube.com/watch?v=BSgeq-EubrU). The whole scene was:

"(Ellen was pretending to investigate the audience to indentify a Russian spy. She picked up a lady and kept questioning her.)

E: Okay you go into the bathroom, you are American.You come out, you are American. What are you when you are in there?

L: European(urinate -ian)?

E: That right! You get it. Wait, what are you when you are on your way in there?

L: I'm a Russian(rush -ian).

E: Yeah you are a Russian!"

Well it took me some time to understand the implications. Then I found it so hilarious that I could not stop laughing, and I'm still laughing as I'm writing it down now. It is really interesting when words become subtle in these occasions. I'm wondering if there are more of these funny word plays. Could you guys post the ones you know below? Thanks a lot!