Video Mania - S3-E6
Plot hole: The plot for this episode is that Mark reluctantly tries out video games for the first time and soon becomes addicted to them. However, the season 1 episode "All in the Family" showed him to already be an avid gamer.
Audio problem: When Cody is playing the blues on his guitar, he is shown to be fretting the higher pitched strings while playing the lower strings open. However only low notes are heard and at least three different chords are heard, which would not be possible if he was playing the strings open.
Answer: According to the SBS website, Brendan's disappearance was never really explained. He just kind of faded out. He was hired as the cute "little" one and as he got older he wasn't as cute. When the Lamberts had the little girl, they got their cuteness factor back and didn't need as many kids around.
Carol and Frank continued to tell people they had seven children throughout the remainder of the show's run, but they never referred to Brendan after season 6.