So when I was like level 15 I took the Castle mission which ends with you facing a really difficult enemy(trying not to spoil). I decided I was too low of a level for the mission so I fast traveled and did other stuff. But for some odd reason Preston went with me, so I now have him and whoever else I choose to be my companion.

He still fights and everything but he is severely limited. I cant talk/trade with him("We need to focus on taking the castle back" is his canned response). I cant stimpak him and I can't get rid of him either. You can pickpocket him though which is funny. Since he is in your vicinity he does like/dislike your actions.

I was wondering if anyone else had this happen or if it was just me.

It's typical of temp companions to follow you into Hell for some reason in these games

I remember running around with that one chick, Sydney I think, in Fallout 3

As for the Boss at the end of Castle, I gunned it down using the vertibird. Other than that, it sounds like another bug.

Im sure I could take it down now but having two companions is pretty fun, albeit a little too easy.

he is going to annoy you the rest of your Bethesda given game. He's bugged for me but not that bad. Now you can't escape him and his endless repeating quests. if he even gives you them now

What bugged me about it (lol) is that I gave him some useful gear to carry and then he was insisting on taking back the castle, didn't allow me to trade with him or anything, so I had to go all the way there at Level 9 to complete the quest just so I could get back the items I gave him. We should have the option to refuse going to take the castle but still trade.