Dr. John A. Zoidberg isn't always the smartest character on Futurama but in an odd sort of way is the most sincere of all of his crewmates. While others are seeking fame or fortune, Dr. Zoidberg just wants to live a comfortable life and to occasionally make people around him laugh.
Even though his friendship is often taken advantage of by the Planet Express crew, he never holds a grudge. That said, over the course of the series, he has made quite a few dumb mistakes.
Zoidberg Cuts Fry's Arm Off
Zoidberg happens to come from a species where being a doctor is the lowest and poorest of occupations. This means he isn't the most viable mate when it comes to the opposite sex in his homeworld.
So when the normally happy go lucky Zoidberg begins experiencing aggressive tendencies towards his friends, it is found out that hormones were the culprit. After being given the opportunity to mate with the love of his life, he found out that she desired Fry more, leading to Zoidberg cutting Fry's arm off.
Poppler Craze
If there is one thing that Zoidberg can teach all of us it is to always examine what you eat before putting it in your mouth. After the Planet Express crew come across a tasty delicacy on a faraway planet and bring it back to earth to sell for profit, Zoidberg becomes addicted to these popplers, eating buckets of them a day. This proved to be genocidal as these tasty treats turned out to be the babies of a ferocious alien species.
Signed Up To Mercy Kill Professor Farnsworth
The idea to never swear to murder a friend if they come down with an extremely deadly or contagious disease is probably worthy advice to take to the bank. Sadly, because of Zoidberg's kind heart and overzealousness for a friend, he did not heed to such a common-sense message.
After Professor Farnsworth contracts yetiism from a savage yeti, Zoidberg agrees to kill the professor if or when he succumbs to the disease. Thankfully, the Planet Express crew managed to find a cure.
Grafts Fry's Head To Amy's Body
It is never smart to mess with the natural laws of science. Even if it is to save a friend's life. After Amy and Fry invite Zoidberg to go on a trip with them, Zoidberg accidentally tears apart the steering wheel resulting in the car crashing, mortally wounding Fry.
Upon waking up, Fry learns that his head had been grafted on to Amy's body until Zoidberg could find a way to place it back on his original body. This split decision ultimately led to Amy and Fry breaking up.
Sold All His Planet Express Shares For A Sandwich
Everyone has had times when they were so hungry they would give all the money they had for some food. Though, after satisfying this hunger, remorse for doing so would sink in.
Sadly, in Zoidberg's case, when Planet Express was taken over by a formally frozen and terminally ill 1980s stockbroker named Steve Castle, the crew were distraught by the takeover but elated to know Castle still didn't have majority control, at least until Zoidberg sold his shares to Castle for a sandwich.
Sentenced To Death For Eating Earthican Flag
Even though Zoidberg has lived on earth for years, he still is unaware of the earth's culture and sensitivities especially when it comes to such things as patriotism. In a moment of intense hunger, Zoidberg eats the Earthican Flag in front of spectators at an event celebrating the earth's unity. He is immediately condemned as a traitor and sentenced to death by an angry populace.
Even after being condemned to death by the government of his new home, Zoidberg still remains unaware of what exactly he did wrong.
Stole The Box Containing His And Many Other Universes In It
The most important lesson Zoidberg should learn is to not mess with the fabric of time just because he feels like his friends treat him unfairly. Luckily, this is a lesson that none of us will truly ever get to experience but just to be on the safe side it is always best to reiterate.
When Zoidberg meets an alternate reality version of himself, the two steal the universes that Dr. Farnsworth created and placed in a box. Which ultimately almost led to the destruction of countless lives.
Lived Like A Big Shot After Being Given Three Hundred Dollars
Zoidberg has made some serious mistakes in his life but usually, these mistakes are out of some form of blissful idiocy. However, when Zoidberg is awarded three hundred dollars by the government, Zoidberg believing himself to be set for life soon forgets who his friends are.
It is only after he is mocked by Mom that he comes to understand that this amount of money isn't endless. As a means of trying to atone for his past transgressions, he uses the money to buy homeless people meals.
Gave Up His Dream Of Being A Comedian To Be A Doctor
Dreams are often hard to accomplish. That is precisely why so few actually achieve great heights of success in their chosen field of occupation. That said, for the few that strive to obtain their dream job no matter what others say, those are the individuals who most often succeed.
Zoidberg's dream wasn't to be a doctor, instead, he wished to be a comedian. However, after being told he wouldn't succeed at being a comedian by his family, he decided to pursue a career as a doctor.
Treats Humans Even Though He Is Unfamiliar With Human Anatomy
Most people when obtaining a college degree find themselves quite familiar with the major they achieved the degree in or at least that is the hope.
As far as Zoidberg is concerned, for a doctor, he is incredibly unfamiliar with even the most basic forms of human anatomy. This is precisely why Santa deemed him the only person worthy of a gift for Xmas as he had committed so much chaos through botched surgeries that the homicidal Santa respected his body of work.