Use the Sucker to Linus and he will give you his Party Invitation. You will also get the pen when he leaves. This Sucker is a Lemon flavored, which is Linus’ favorite.
How to Get the Sucker
You need to get first the Trick or Treat Bag, run outside into the street and find Pig Pen. He’ll tell you that he can’t come to the Trick or Treating because he doesn’t have a Trick or Treat Bag, good thing that you have one. So give him the trick or treat bag and he’ll give you a lemon flavored Sucker. This is Linus favorite by the way.