Character mistake: In "I Heart Dancing", the lady at the Krusty Krab tells Spongebob the dancing audition is the next day. Later, Spongebob is practicing at Squidward's house for a whole night, and the next morning Squidward says they have one more day to practice, even though the audition should have been that day.
Character mistake: Will's tax demonstration to his volunteer staffers is incorrect. He applies the various tax rates to the entirety of each salary range. The person who makes $150K and is in the 36% rate...in his example he has them paying 36% on their entire salary, not just the portion of it that puts them ahead of the next lower tax rate. If the tax rate jumped to 70% at income of $1M, and a person earned $1,050,000, they wouldn't be paying the 70% rate on all $1,050,000 of their income, only the last $50,000 of it. Will's example makes it look like they would be.
Character mistake: At the end of April and the beginning of May in 2004, Luis was decoding the CDs with the Crane secrets on them. For an extended period of time, Luis left the CDs completely unattended at Hank's house. Luis told several different people that the computer was decoding the CDs and didn't need anybody there to do it. Given that Alistair is virtually omniscient in Harmony, it's ridiculous that he didn't break into Hank's apartment and take the CDs.
Character mistake: The fetus' blood type was AB and the mother had a known type of A. So Dr. Huang said the Father had to be type B which is not completely true. The father could also be type AB as long as he had a single chromosomal copy of the B allele, which any doctor would know. During meiosis only half your genetic DNA is passed on to the offspring.
Character mistake: When Tony tells Dr. Melfi he feels as though a safe might fall on his head, she replies, "a feeling of pending doom." A woman of her intellect and education should know the proper word is "impending." "Pending" means something awaiting a conclusion. "Impending" means about to occur.
Character mistake: In the final episode, Carlos visits Doc in the psychiatric hospital for advice concerning his upcoming marriage to Holly. While talking, Carlos refers to Doc's deceased wife as "Linda", while throughout the series, it has been made very clear that her name was Deborah.