"Transform?" Mary whispered the question almost passed out from the brutal fucking she just received from her insanely hung sister.
Jen figured that was close enough and shrugged "For your transformation you will grow an 18ft horse cock tongue and your breasts will act as your balls. Every time your name is called your cock will become erect and double in size!" Jen said the last part with huge excitement as she watched her preteen sister start to transform. A monstrously huge horse cock pushed its way out of her tiny mouth growing longer and longer reaching her feet and it kept going slithering across the floor of the room until it reached the 18ft length she specified. Then Mary's non existent tits started to swell reaching the absurd size of beach balls on her tiny body "Holy shit!" Jen whispered even as her own cock started to grow as she became aroused looking at her sisters new cock and massive tit/balls.
"What the fuck did you do to me Jen!" Mary whined making Jen rock hard and surge a foot more in length. Jen glared at Mary before jerking her massive cock off and pointing it right at Mary covering her in her massive load. As Jen's cock softened she whispered at her sister "That wasn't very nice...Mary" and watched as her sister's behemoth started to grow. It grew to an insane 45ft before it jerked and swiftly doubled in size to 90ft of horse cock protruding from her 9 year old sister's face.