Bootleg Warning : Nendoroid Mikuru Asahina (Good Smile Company)
Below is one example of a bootleg figure, please note that is is only one possibility. You should always be on the look out for anything suspicious.
Also note that there can be bootlegs of various figures, not just the examples shown on this website.

On the official version, the Mikuru Beam parts are a transparent green, while the bootleg is solid green.

The official version has a blush on the cheeks, while the bootleg version does not.
Also, the bootleg has black eyebrows when they should be brown as they are on the official version.
The bootleg version also has a very shiny, glossy look to it when compared to the official version.

The JAN code (see image above) uses a different font on the bootleg version. The left side is the official font, and right is the bootleg version.

The product images on the box are much rougher and grainier when compared to the official version's box.

The inner flaps of the box on the official version include assembly instructions, while the bootleg version has nothing.

The back panel of the box both have a 'Nendoroid' pattern in the background, but the bootleg version is very faded and difficult to make out.
(The official version makes it easy to see the background even on inside the box.)

The bootleg version does not include the copyright, while the official version reads "© 2006 谷川流・いとうのいぢ/SOS団".