"... horses." Kate finished before waiting on their reaction.
Tom heard her while watching his ring, middle and index finger starting to merge on either hand while an odd rubbing between his ass cheeks was just the puckering of more equine anus. He couldn't help but feel faint.
"Th-this can't be real or happening or, or, " but Tom could feel his ears burning and as he spoke he moved his merging hands to his ears where he felt not only a point, but the growing out of the ear itself. He pulled down his hands and sat back on his bent knees. His chest was heaving while his thighs and ass appeared to have gained girth of muscle and fat. Tom tried to ignore all this and spoke carefully, "I do not want to be a stallion so pl-please stop this trip or dream or whatever it is."
Meanwhile Matt struggled with his own swelling, with what he knew were his balls feeling hairy before expanding while still in his pants. This only caused him to go hard before cumming, soaking his jeans, while his cock only got thicker, darker, and partially sheathed. So by the time Kate looked, shaking her head at Tom's request, to Matt, who had 29 inches of mottled horse cock now poking out from his waist while Matt lay on the bed.
"Well, the spell can't be reversed and you're not the stallion, Tom. Matt is," she said looking impressively at Matt's growth.
Tom turned as well and couldn't believe it. Matt went red but he was otherwise looking darker skinned all over, hairier as well while all his clothes were somewhat strained. Of course in the middle of it was, especially with his belt and button finally giving way and showing Matt's very equine looking package that was still on the grow.
"But if he's the stallion then what would I do?" Tom asked, feeling a twinge in his taint at the same moment.
Kate tried not to make eye contact but came to it after a long breath. "Well you were supposed to be my ex so I had wanted him to take it so I'm sorry again but you'll be something like brood mare."
As if to counter this point, Tom's cock went hard, tenting in his strained pants and filling him with some pride before he felt himself starting cum but without any excitement or release. More like it was just trying to leave his body. Tom wanted to stick a hand down to see what was happening but now his hands had started to darken and harden. "No I, I," Tom tried to reason while ill-feelings and nausea accompanied what was the forming of all the bits of a virgin mare.
"It's okay, you'll be fine," she tried to say while Matt fell to floor on all fours. She figured this might be best for both of them now.
She walked over to Tom and helped ease him forward onto his hands, now more akin to hooves. Soon as he was, there were popping and cracking noises from him, and Matt, as their bodies took to their new position. Kate took the opportunity, as Tom's clothes shredded, to pull away his pants. His revealed backside caused him to shudder when cold air hit him.
"What's going on back there?" Tom asked, his neck stiff. Kate fumbled for a moment, there was a flash, then she came around to the front of him, holding her phone.
"I took a picture. See," and she turned to show the backside of what could very well be a shaved horse. "See, your tail is starting here, you poop from there, pee from his hole now," she said with a finger, "and horses fuck you here." The final one nearly caused Tom to vomit as the look was not only a swelling mare sex, but he could feel it on his backside...
"You better get used to his backside, Matt. You'll see a lot of it," Kate almost teased before remembering something. "Oh, and before I forget. The spell will take you two to a nice farm upstate so no need to worry about that. Parents will be sad but from the looks of your rooms, and being here on winter break, they aren't losing much. Oh, and that way back, it just requires that the mare here gets pregnant so you two will have to consummate this whole... bad situation."