IronYoshi was reading in a spellbook he loaned from Princess Twilight in hopes to try out a spell for fun. Little did he know that the spell he chose was a gender swapping spell. He thought that, because it was a spell for master unicorns, he could never do it, so he tried it.
As he casted the spell, a bright pink cloud formed around him and started to transform him. His hips widened, his "under horn" became a "clam". As this happened he lead out at scream that quickly sounded like that of a mare. His face softend and eyelashes lenghtend, at the same time his chest bulged out to a C-D cup. His shorts became a skirt, his blouse resized to fit his new body, his socks turned into a pantyhose, his sneakers became boots and of course, his underwear became that of a mare as well.

This transformation happened in the span of 5 seconds and was very painful.