All fishers (should) know about the fishing dailies from Marcia in Dalaran. You know, by the pretty well thing. Well, if you don't, then uh, too bad.
I got on WoW. Did my Monsterbelly Apetite daily, and got my reward. After which I decided to do some BGs for the Children's Day Achievement. When I got out of the battle ground, amazingly, Marcia had another daily for me. So I did it. I got my reward, did another BG. Came back. Another quest. So after that I logged out and back in... another quest
Also, this does not count toward your Max Daily Quest thing, so you can do it as much as you want.
I uh, hope you uh, enjoy it. DO IT BEFORE IT DOESN'T WORK. Oh and, I'm not creative, so I can't provide screenshots (screenshots of what, me getting it, and me getting it again, with different times? But oh, someone will be liek "HEY DUDE YOU TOOK THOSE ON DIFFERENT DAYS OMGZ")
TLDR -or- I dont care for this guy's story:
Do Marcia's fishing daily
Go into an instance, BG, log out etc.
Get another daily.
SOMETHING I FOUND OUT: When you take a daily, go into a BG etc, and get out, the daily's gone. So you have to stay in the same zone when you get the daily.
Oh and, I had someone I know try it out, and he said it didn't work. Which, is odd. I don't know I got it to work, but it keeps working and I'm not arguing.