Lenticular printing is a technology in which a lenticular lens

Lenticular lens

A lenticular lens is an array of magnifying lenses, designed so that when viewed from slightly different angles, different images are magnified...

 is used to produce images with an illusion of depth, or the ability to change or move as the image is viewed from different angles. Examples of lenticular printing include prizes given in Cracker Jack

Cracker Jack

Cracker Jack is a U.S. brand of snack consisting of strong molasses flavored candy-coated popcorn and peanuts, well known for being packaged with a prize of nominal value inside. Some food historians consider it the first junk food...

 snack boxes that showed flip and animation effects such as winking eyes, and modern advertising graphics that change their message depending on the viewing angle.