Lululemon alleges that Costco has stolen the intellectual property of its Scuba hoodies and sweatshirts, Define jackets and ABC pants.

Cheaper look-alikes have been around for years, but social media has made them more popular. Dupes can move into shaky legal territory if concerns arise around consumer confusion or patented designs.

Because of this, Lululemon claims this leads at least some shoppers to believe that Kirkland-branded products are made by the authentic supplier of the "original" products. Lululemon claims Costco doesn't try to dispel the ambiguity.