I've seen these at a store in my local mall. It had all the different Kirby's, including these. Was considering buying one or two of them, but I dunno. How do you know these are bootleg?

The big key on finding out for official Kirby dolls (or any of these plushes) should have two types of tags: The little tush tags with the manufacture and trademark (normally on their butt or legs) and the company/logo tag (the paper one you can easily remove).

Also, look at the stitching and ask yourself: is the quality good? Are there any loose threads? Is the threading even? Are the colors even right?

Check online for that same doll and look at the stock photo. Are the accessories attached to it similar to the ones you saw at the mall? Do noticed anything different such as color, placement, size, etc..

Make sure to check your store, are they licensed with some big named company (ie, Nintendo World, Gamestop, Toys R Us, etc.) or are they just a little entrepreneur shop? The named brand shops will guarantee that you're getting the authentic item and of course, charge you tax but the little ones usually don't do either.

If you're buying online, always read everything the description says. If you're buying on eBay, there's a high chance that the item is bootleg.
Things to look out for:
Location - Hong Kong
I hate to say this, but Hong Kong is known to be the king of bootlegging, plush included.

Rarity
If they claim to have a lot of a rare doll, normally UFO ones, there's a chance that they're selling you fakes.

Stock Photos
Unlike looking at stock photos and compare them to real life, this one is a thing to look out for. Normally, they just grab a picture of the internet and claim that their plush dolls are similar to the ones you see.

Pic related, they're the stock photo version of the plush I have, and are actually authentic.

(I should make this into a Sticky Guide.)

Thanks Zippie, I'll keep a mental note of those factors next time I'm able to visit. The name of the store is called "Niko Niko". Not a huge company but its getting a bit larger. It's basically a little anime store also carrying the well known Video game items like Kirby, Mario, Zelda..etc. That sort of merch. I'll try not to look too suspicious when analyzing their rack of Kirby plush's :P

>>192 Yes, you should.
>I should make this into a Sticky Guide.