Hold them in your hands!
The first thing that “pop” in my head when I read an email from my friend : I want to have those bags!
Do you feel like getting one (or few) of them as well? You will realize that those companies not only create the desire to purchase their products, but also the desire to actually get their bags! Because the marketers make the bags so nice to carry around, it does provide some sort of post-purchased satisfaction to customers. I would certainly love to shop at those places if they do provide me those cute and funny bags.
Also, making the bags hilarious and funny to be carried around is one of the brilliant ways for companies to advertise on their products as it is way much cheaper to advertise on bags than on television, newspapers, magazines, billboards, etc. The coolest thing of adopting this advertising strategy is that they actually make customers speak for them by carrying the bags around! How simple it is to distribute powerful messages to potential customers who has similar tastes as the purchasers (people with similar thoughts, values and thinking styles will most likely work or get along, don’t we?) in a low-cost yet effective way.