I know him! We'll sort of be did that to mine too. I think he just trying to make friends or something. He used to do that on my wall as well I think he is trying to make friends because I did reply back before and he said a few things although the llama are confusing to me. Or why he sends them instead of actually talking.
I stopped replying because it is very confusing and I don't have a lot of time to keep randomly replying to llamas? and he stopped.