Shining Armor had something to prove to both himself and his wife. Diapers weren't a neccesity, he wasn't a forgetful little foal. It was demeaning enough that he'd been given a little pony potty to use (although some part of him reveled in the effort put into shaming him). The need to go was unbearable to the point he did a potty dance in the high chair until he was allowed to flee to the restroom. Once there, Shining sat down on the potty and released, sighing as the pee was allowed to flow.

Warmth spread over his privates and his eyes widened when he realized he'd made a terrible, horrible error, one that would result in much teasing and diaper pokes for years to come. Lifting his skirt and looking down revealed the terrible truth; He'd forgotten to take off his diaper.

"Well, well," Cadence teased from the bathroom door. "Looks like poor iddy biddy Shiny Whiny forgot to take off his diaper. But that's okay, widdle foals make siwwy mistakes wike dat~" With a smirk and a giggle, Cadence levitated the extra thick, extra strength diapers she'd threatened him with earlier. "Looks like you'll be in diapers for a long, long time. That poor skirt will never hide your puffy widdle tush!"
Groaning, Shining pulled his skirt back down, that last time he'd be able to hide his diapers from his wife for a long, long time.

//Little cute story by  theconflicted who is writing the fanfic that gave me this idea.