I spent the earlier part of Halloween this year in a plane, flying back from a job in Milwaukee. I didn't quite finish this doodle, but you can clearly see what a difference strong, bold lines make. No need to have a big broad tip marker to go big and bold, though. This doodle was done with a regular ball point pen I bought in an airport snack shop. If you keep adding to a thin line, eventually you get a thick one!