The patterns are made by different diffraction gratings in the caps. If you put them in front of another laser you'll get more or less the same effect.
About the laser, 17$ is a fairly high price to pay for a 5mW greenie. You can probably find one of ebay for around 5$. Also, the reputation of Tmart isn't very good. The reviews are likely genuine since I don't think Tmart will pay people to give its product bad reviews. I also don't think members are bored enough to come up with bogus bad reviews just to give a company a bad name. These reviews are made by people experienced with lasers and if you look in the review section you can find many.
One thing to keep in mind is that these cheap greenies are overspec in many cases and are over 5mW so you may need goggles unless you have a LPM verify that it is under 5mW. Not pointing at people or air planes is obvious. If you want to scare birds 5mW of green is more than enough but I wouldn't suggest it because you may hit the bird in the eye by accident. I don't think you would want to be blinded and neither do a bird. If you use a diffracting grating with a low power laser it may be ok to scare the birds as long as you are far away since the beam is dispersed.
