There is nothing graphic in chobits, and so the sexual references will most likely not even be noticed by younger children.
Hideki quite frequently has sexual fantasies/dreams about girls he knows.
An erection joke is made.
References to porn are occasionally made.
Chii's "on" switch is her crotch.
Chii is occasionally seen partly naked/completely naked, although there is always objects on the screen to block it.
When Hideki and Shinbo are at an indoor hot spring, Hideki stands up out of the tub naked, although you can't see his genitals.
On two occasions, people try to touch Chii's private area.
Chii tells Hideki that she loves him and that he can 'touch her'.
