hi i need to know where to fish in hat head lake i have nearly finished the mad scientist castle

The quest should tell you exactly what to do to get that .
Have you read the writeup in your Quest Log? If you don't read the writeup as you accept a Quest, this Log is always there until you turn it in, and then it's still there for 5 days after you turn it in.
And perhaps the Maps 'Show Active Quests' should show you what particular square or squares that any particular quest needs you to go to.

I can't remember that one, but wasn't that one your fishing up that Hat?

Check your Inventory of Hats to see if you have it. If you have it, then you have to wear it at least for a little while.

Yes, until you complete the Pyramid.
That's really tough luck for you. The pyramid is 8 squares big.

Bring up your map, go to the pyramid zones and click on 'show active quests'. When the left hand side of your map shows the quests, click on them and READ what it says. That will tell you what you need to do to get rid of the brain slug. You can us this feature for any quests you may have to do except one, which I can't remember just now. In any case it is a handy feature we have had for months now.

I just wish I had done the slug one around Halloween instead...it would have been cool to wear then.