How about yuri dom/sub relationships between lolis.
I've been thinking about a situation where two girls in the same class are close friends. One of them is smart and competent while the other one is a bit stupid and immature, but it's actually the dumb one who plays the dominant role. The smart girl is naturally meek and docile, so she finds it very easy to let her friend take charge and boss her around. In fact, she almost never says no to any request or suggestion from the other girl and even happily takes responsibility for mistakes she makes or trouble she causes.
And one day, while they're at the baka's house, the smart girl finds out her secret that she still wears goodnites because of occasional bedwetting. The dominant girl is very upset, so her friend offers to wear one to make her feel better. In the morning they're still both dry and both need to pee, but after using the toilet herself she orders her submissive friend to pee herself. Of course she can't bring herself to say no.
One day the dumb girl forgets to change out of her wet overnight pull-up and comes to school wearing it. After homeroom she drags her friend to the bathroom and insists that they swap underwear. A few minutes later they walk out together, the dumb one with a smug look on her face and the smart one tugging on her skirt and blushing from ear to ear.
This kind of thing continues until the smart girl who has always had excellent bladder control has faked having a bedwetting problem and started wearing pull-ups every night and even sometimes during the day to make her friend feel better.