I was playing yesterday (MP) and I was having lag (200+? maybe) and something happened: a alien came out of nowhere and tail leashed me, sending me flying at an hi velocity, to the other side of a huge room. Thing is I think the lag made this error occur. Or can this happen in a normal situation?

No, this is definitely due to lag. However, I cannot say whether this is lag on your end or if the other person was lagging.