Facially, it means toad worship. In China, toad implies previous president Jiang Zemin. So 膜蛤 means Jiang worship, which is very popular on Chinese websites but banned by the government.
膜蛤的人叫蛤丝，也叫膜法师，这种人通常都会念两句诗 苟
by Philosophy♂ King February 5, 2017
Get the 膜蛤mug.