Continuity mistake: During the scene with the family in the living room and Claudia and Lily are sitting on the covered couch, the sheet falls off the top of the couch. In subsequent shots the sheet falls off and goes back on the top through the whole scene.
Continuity mistake: When Sean and Claudia catch Lily doing homework in her room, and they realise that she is not actually drunk, Sean asks where she was "tonight." But downstairs, a few minutes ago, Sean commented on her being drunk in "the middle of the day."
Your Father Should Know (2) - S4-E2
Continuity mistake: In this episode, Claudia states that she was seventeen years old when she first had sex. In the season one episode "Like a Virgin", it was revealed that she was fifteen.
Pay You Back with Interest - S4-E7
Continuity mistake: In the episode where Eddie first gets his blue electric car. He plugs the car into the kitchen with a long red extension cord. When there's a shot of Claudia first coming out of the kitchen to see what's going on, the red cord is gone. The whole kitchen entrance is shown, so the red cord should be visible. Then, when Eddie and Shawn are shown again, the red cord is back on the floor behind them.
Pay You Back with Interest - S4-E7
Continuity mistake: In this episode, Lily's golden sprite tattoo is underneath the name "Dean" - "Dean" is written above the sprite's head, between the tips of her wings. A few episodes ago, at the end of "Your Father Shoulder Know - Part 2", Sean hugged Lily and accidentally lifted the back of her shirt, revealing the tattoo. The name "Dean" was not there.
Suggested correction: People don't always have the time and/or money for a tattoo of that size to be finished in one session. Dean's name was simply not added yet. Or, since the sprite appears to be finished when Sean hugs Lily, maybe Lily had not yet decided to include the name.