Hannah Montana Season 2 Episode 19

When Robby and Lilly's mom Heather make plans to go out on a date, Miley and Lilly get so excited, the're sure they'll hit it off and the two of them will become sisters, but all doesn't go as planned when Robby and Heather have a disagreement and the girls argue over whose parent is to blame.

http://www.imdb.com/title/tt0493093/episodes