The moment Twilight's hand first makes contact with Applejack's bottom there's a shift in the farmgirl. Her defiance vanishes and she immediately starts crying, but at the same time she also blushes deeper than she ever did from the vibrations

“I hope that gets you to behave. If not, I will make the torture even worse.”

Applejack simply moans a mixture of pain and pleasure, it also seems that after being spanked she's start to leak a bit of pre-cum.

"Hey Twilight," Rainbow Dash says from her high chair. "Since I gave you that tip to make Applejack behave do I get a reward?" She asks hopefully.

“No.” Twilight said firmly. “Sit through this treatment with good behavior and then, you will get a reward.”

"Aww," Rainbow pouts, but then starts to squirm a bit. "Can I at least get a fresh diaper? This wet one's starting to itch a bit." At this point the diaper hanging off Applejack's reddened bare bottom is also pretty soaked.

“Maybe later.” Twilight said, a little annoyed.

"Aww come on Twilight," Rainbow Dash whines, and starts to give her a bit of puppy dog eyes. "I've been good haven't I? What more do you want before you'll at least change me?"

Applejack at this point is simply still laying and panting, her own diaper still hanging down off her bottom.

“Soon. For now, just get used to it.” Twilight said, pulling Applejack’s diaper back up and sitting her back down. “Now, finish your food.”

Rainbow pouts, but proceeds to eat again. Applejack for her part stops panting and looks up at the baby food on her highchair tray. After looking from it, to Rainbow, to Twilight, she sighs and starts to eat as well, retching after each bite.

Twilight gave them each bottles after they finished.