Mr. Plankton is a dark comedy-drama about a young man who was abandoned by his dad after he learned that the kid wasn’t his son. This isn’t your ordinary cheating story; Hae-Jo, who used to be known as Choi Seung-Hyeok, wasn’t born an ordinary kid. I mean, he was born normal, but from his dad’s frozen sperm, because his dad had testicular cancer and he was desperate for a child. After Hae-Jo’s dad was cured of his cancer, Hae-Jo’s parents decided to have a child. But, when the kid’s 8, he’s desperate for a sibling, and this has his mom considering the possibilities. When she makes a call to the clinic that helped with Hae-Jo’s birth, she learns that the kid isn’t her husband’s but a random donor’s. This leaves her devastated, but she decides to hide the truth...