This isn't a cosplay per se. It is a Snorlax dress. Different!
Over on website Deviant Art, ~bethanyagogo made this Snorlax pocket monster dress because her friend had a Pokémon-themed party.
"I made the dress out of fabric from two XXXL t-shirts [one in dark teal and one in tan]," she writes. "I screenprinted eyes and mouth, appliqued the tan pieces onto the teal fabric, and sewed it into a strapless bubble-hemmed dress."