These pokemon can only be caught if dawn sister says so you can find her at Sandgem Town in your rivals house the pokemon are
Doduo
Zigzagoon
Cubone
Nosepass
Phanphy
Dunspacrce
Snubell
Absol
Spoink
Drowzee
Swinub
Voltorb
Farfetched'd
Skitty
Natu
Makuhita
Krabby
Spinda
Beldum
Pidgey
Corsola
Surskit
Smoochum
Likitung
Magnemite
Electrike
Slakoth
Tangela