“…Show-off.”
“But yeah… she’s pretty good.”
“Still stuck on that boss?”
[Montage of their childhood – losing TV remote batteries, splitting the last pudding, covering for each other’s lies to Mom.] My Little Sister is Pretty Good -Final- -DomiHo...
“You said it yourself, big bro.” [She smirks.] “My little sister is pretty good.” “…Show-off
It looks like you're referencing a specific title or fan work: splitting the last pudding