Have you ever seen any 3D illusion pictures before? If you did, then you should know how to spot the hidden things in a picture. If you not, then you should try it because it's a fun experience!
Ok, firstly, try to concentrate on the center of the picture, cross your eyes a little bit for a few minutes and you will see a big 3D penguin in the middle of the picture.
If you still cannot do it, then put your index finger in front of your nose, and keep all the concentration on the picture, you'll see it.
Here is the picture:










