When the Silly Nannies sing "If You'll Marry Me," they are holding string, and skipping around. When they all stop momentarily, watch them. When they start skipping again, their numbers change.
When Stewie hits Brian with the chipping putt there's obviously blood over the carpet, then Brian moves on telling his fake mustache is $2.99 and Stewie shot him in two knees and obviously more blood was on the carpet, but when Stewie uses the flame thrower to burn Brian the blood on the carpet has just magically disappears.
During the second beating scene, Brian can be seen running from Stewie and the stairs are clearly seen behind him. However, Stewie still runs over and is able to push Brian down them.
The Alan Ayckbourne (sic) play that they go and see is held in the 'West End Theater' using the American spelling of 'Theater'. It should be the British spelling of 'Theatre'.
In England, Lois is watching BBC 4 in the middle of the day even though BBC 4 doesn't go on air until 7pm.
When Lois, Meg, Stewie and Chris go to the theatre to see a purported Alan Ayckbourn play, the marquee misspells his surname as "Ayckbourne."
In the episode "Patriot Games", Peter identifies himself as a "secret-agent astronaut millionaire" at his high school reunion. Shortly after it is revealed he works at a brewery, Tom Brady mistakenly thinks Peter claimed to be a "cowboy astronaut millionaire".