Some Polish people start imitating English. What are their reasons for doing this?

Sometimes when I'm walking in public with my friends (speaking English) I notice randomly some people start imitating words or phrases. Most recently somebody imitated "I think so too...hahahahaha" after my friend said it loudly. It's really annoying, I hate their horrible accents and I want to know what are their reasons for doing this?

probably making fun of you and your chavvy mates

Wow I don't have any "chavvy" mates, maybe you do! ;) I guess its just ghetto Gdansk, I don't have this happen to me in any other polish city.

I've had experienced this abroad before - but not in Poland as it happens.

Just young people messing about with what they think "sounds funny" - to be expected sometimes. I don't think it has particular significance in that it is English they are making fun of or that they are in Poland.

Because the think they are better at English than Polish?
No smart answer, really.