The sign the dog is holding says "Always think ahead", like in the CM.
Oh this is going to be hard to explain to people not living in japan, but I can say that this movie is like a parody of a japanese TV commercial.
If you go to this page you can watch it http://www.aiful.co.jp/f
/cm/PF60H010.html AIFUL is a company that lends people money with crazy high interest (like 30% or so) and basically what this CM tells people is that they should think ahead before they borrow money so that they won't get in trouble when it's time to pay back... The sign that the dog is carrying says something like "Always think ahead"... that's about it I think.
This movie is about that guy in the CM, but in this movie it seems he borrowed a little too much money, and of course the dog is there as always, only with a twist.
Now enjoy the movie!