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.