Here is my video on every reused costume on Dance Moms. I am going through each season, so this video is just season 4 only.

Introduction - 0:00
Episode Special, "Guess Who's Coming to the Dance?" - 0:06
Episode Special, "Dance Moms Cares Special" - 0:27
Episode 4, "Chloe vs. Kendall: Round 2" - 0:49
Episode 9, "Nothing's Fair in Abbysville" - 1:11
Episode 10, "No Solo for You" - 1:32
Episode 11, "Blame It on the New Girl" - 1:54
Episode 12, "Sister Showdown" - 2:15
Episode 13, "Decisions Decisions" - 2:56
Episode 14, "Family Comes First" - 3:37
Episode 15, "Lights! Camera! Dance!" - 3:58
Episode 16, "Presenting My New Team" - 4:38
Episode 28, "Another One Bites the Dust" - 5:00
Episode 32, "Playing Favorites" - 5:22