What are Gags?

I just read a posting here about Gags. What are gags and are we supposed to be collecting them. From reading the thread about them it sounds like we're supposed to be collecting these random appearances on screen. Please explain.

I found the answer to my question! Searched this forum for the word Gag and found all the related postings for it. Now I have something else to do with this game. What an awesome and fun game!