16 The total number of children Cletus and Brandine have is 44.

Cletus is depicted as someone who doesn’t care much for what other people think, especially about his relationship with Brandine, who is a relative. Though Brandine is represented as his wife, the actual nature of their relationship is rather vague in the show. Brandine is sometimes seen or referred to be in labor during the show, bearing more children. The couple are also known to give their children strange names like Condoleezza Marie, Rubella Scabies, Birthday, Crystal Meth and so on, to mock pretentious celebrities who give unorthodox names.(source)

17 Lenny and Carl both have a master’s degree in nuclear physics.

Lenny and Carl are two supporting characters who are the best friends of Homer with a master’s degree in nuclear physics. All three of them work at the Springfield Nuclear Power Plant. Lenny and Carl are very close to each other and are rarely seen apart in the entire show. Homer almost always confuses Lenny and Carl, and even has to write down who’s who on his hand so that he won’t forget.(source)

18 The Couch Gag was originally designed as a time-filler. If an episode is long, then the couch gag is short, and if the episode is short then the couch gag is long. 

Couch gag is a running visual joke in the opening sequence of The Simpsons, depicting the characters in scenes of outlandish and absurd situations. Sometimes the couch gags are new, but most of them are repeated. The longest couch gag so far has the Simpsons family forming a chorus line with dancers while their living room background gives way to reveal unicyclists and elephants. Known as the “Circus Line couch gag”, it was used when the episodes were in danger of being too short.(source)

19 “Do the Bartman” topped the charts of Australia, Ireland, New Zealand, Norway, and the United Kingdom. The song was co-written and co-produced by Michael Jackson, who also provided background vocals for it. 

Though the producers initially denied that Michael Jackson was involved in the song, Groening later confirmed that he was in fact involved. He could not be credited for the song because he was under contract to another record label. Jackson was also a fan of The Simpsons, especially the character Bart, and had called the producers to write a single for Bart and to guest star in the show. That was how “Do the Bartman” song came about and he starred in the episode “Stark Raving Dad”.(source)

20 The Simpsons predicted Donald Trump’s presidency, the outbreak of Ebola virus in Africa, Higgs-Boson particle, and the Arab Spring.

In the episode “Bart to the Future” aired in 2000, a fortune teller gives Bart a glimpse of the future in 2o30 when Trump leaves the White House after his tenure. By that time America suffers great financial loses and mismanagement, and becomes dependent on aid from Europe and China. Similarly in an episode in 1997, Marge is seen holding a book titled “Curious George and the Ebola Virus”. In the episode “The Wizard of Evergreen Terrace”, Homer is seen to approximately calculate the mass of Higgs-Boson.(source)