In one episode Joey goes to amateur night at a comedy club, but gets interrupted by Phyllis Diller who takes his place. It may seem like a random guest star until you know that Diller lived in San Francisco for part of her adult life.
When DJ gets her first car, Danny plays the song "The Horn Went Beep Beep Beep" on the guitar. It may look like Danny looking like a dork, but in a previous episode he had an attachment to his old car and the song had some meaning to him.
Danny being able to buy a new car in a season one episode, renovate the entire basement twice, as well as take vacations (when his roommates don't pay rent and he lives on a local TV newscaster's salary) makes more sense if his late wife's life insurance paid for it.
Becky announces she's pregnant in the season four finale, which is set in May. It's also established she has the twins in November. This might seem like a standard TV pregnancy, but her and Jesse got married on Valentine's Day in February. The twins were conceived then.
Jesse is Greek, thus his sister, the girl's mother Pam, would have been too, yet in a home movie Pam is shown to be blonde. It's odder still that the girls would then be half-Greek and their dad has dark brown hair, yet they all have light hair.
One episode had the family's Greek relatives visiting and all of them were brunettes, which only adds to the confusion.
Clearly Pam has dyed hair and Joey is the girl's real father.
Originally, the Katsopolis family was Italian. Don't know if that helps.
In 7.10 "The Prying Game" Danny mentions that Jesse is half-Greek, making the girls and the twins only one-quarter Greek. Still doesn't explain Pam's blonde hair or how all 5 children in the house inherited blonde hair too.
Don't forget the twins having blonde hair. Me thinks Becky had an affair with Joey.
Some Greeks have blond hair— Cleopatra, for instance was a Ptolomey (Greek dynasty in Egypt) and some believe she was blond and green-eyed. Not to mention, a lot of different genes contribute to hair color, so it could be recessive or something.
I have a cousin who is half Greek and his daughter has sandy blonde hair.
Jesse loves classic rock, especially Elvis. In one episode Danny wanted to sing "My Generation" by The Who with the band for a school function. Jesse said the song wasn't hip enough. Why would he object to that when he sings Elvis and other hits from the 1950s and 60s?
He's an elitist douche who considers himself the final arbiter of cool, that's why. He only says it's not hip enough because Danny, king of the lame, suggested it.