It's almost Mother's Day.  Scootaloo comes to Rainbow Dash with a startling question, but then backs off, feeling ashamed she asked it.  Rainbow Dash, taken off-guard by the question, starts to question both herself, how she feels about Scootaloo, and about her past...

Source

Everypony has someone who cares for them, and has a place to call home. Everypony except Scootaloo. When the forces of nature come crashing down on a cold night, Scootaloo takes refuge in the only place in Equestria she can call home: The Cutie Mark Crusaders' Clubhouse, dark, empty and cold. Frightened and feeling trapped, only the arrival of a young mare with a mane and tail of rainbows can settle the filly. Scootaloo will soon discover that sometimes, the pony who means the most to you as an aspiration, can also be the pony whom you take refuge with at the end of the day.

Much Scootalove. Cause, obviously, Dashie is best surrogate sister~

Sweetie Belle gets curious about where babies come from, so she confronts Rarity about it.