"Big bwothew! Big bwothew!"
Lemonade's eyes slowly creeped open, the shiny Meowstic needing to blink a few times before the dream he had been having finally subsided, and he could completely wake. He sat up groggily, squinting for a few seconds until his eyes could adjust to the pre-dawn darkness.
Standing next to the young psychic-type's bed was what Lemonade could just make out as the shape of his little sister. The Espurr toddler was hopping from one foot to the other, one paw pressed to the front of her pink disposable pull-up, the other to the back. Her magenta night shirt swayed with each hop.
"Big bwothew! I gotta go potty!"
No sooner had the words left his sister's lips than Lemonade became acutely aware of his own urgent need to relieve himself. Darn, he had been doing so well, too! Though he had needed to pee rather badly earlier in the night, he had managed to ignore it long enough to be able to fall asleep. Now, though, the urge was back, and stronger than ever. If he wasn't awake before, he certainly was now! He groaned and moved a paw to the front of his light blue pajama shorts, which matched the pajama shirt he was also wearing.
"Milk! Ugh, why'd you have to get me up for that? You can use the potty without me, ya know," the yellow and white Meowstic grumbled.
"Uh-uh! I don't wanna go out dere all by mysewf! Gwamma's house is too spooky at night! Pwease go wiff me!"
Lemonade frowned. Of course he knew how spooky his grandma's house could be at night - it was the very reason he hadn't gotten up earlier. This was exactly why he hated staying over at her house every summer. 
He shook his head. "Ugh, well, couldn't you have just, like, held it or something?"
"I did!" the little Espurr whined as she continued fidgeting, "I helded it fow fowevew! But I couldn't sweep, and now I weally, weally hafta go pee pee an' poo poo!"
"Well, uh..." the young Meowstic replied, biting his lip, "I really gotta pee, too, but...I just don't want to go out there right now. Maybe we can both hold on a little bit longer? I think it's gonna be morning soon."
Milk frowned. "Noooo! I gotta go wight now! I'm gonna have an accident!"
Lemonade clenched his paw to his crotch a little tighter. He sighed, begrudgingly nodding. "I guess you're right... I don't think I can hold it for that long, either." 
He slowly got up and grabbed his sister's paw, leading her to the door of their room in short, slow steps, each young Pokemon firmly pressing a paw to their own crotch. Every little movement caused the two to quietly moan, and it took them a minute to finally reach the door. Right as Lemonade started reaching for the doorknob, Milk pulled away and squatted.
"Unf! S-sowwy..." she said with tears in her eyes, as a light hissing sound became audible. "I c-can't howd it any mowe!" The bottom of the little kitten's pull-ups started puffing out, the yarn ball pattern rapidly fading to purple smudges across the bottom, back, and front, as more of the garment became heavy and wet with each passing second.
The distinct smell of ammonia became noticeable. As he watched his sister relieve herself, Lemonade instinctively moved both his paws to his crotch, and crossed his legs tightly; it was all he could do to keep from succumbing to the same fate his sister had.
Milk quietly cried as she continued having her accident. After a few seconds the hissing subsided, with most of the garment soaked now: the pull-ups were puffed out from back to front, with none of the fade-away patterns remaining, save for those right by the waistband. The young Espurr remained in a squat, her tail raised. Her whimpering and sniffing turned to groans and grunts, the sadness on her face replaced with strained concentration. A loud "frrrtt", followed by a crackle, accompanied a large bulge appearing in the bottom of the baby pokemon's pull-ups.
"Oh, gross!" Lemonade groaned through clenched teeth. He waved away the thick smell that had accompanied his sister's messy relief with one paw, while the other still clenched his boyhood through the front of his pajamas.
Milk kept pushing, the bulge in the bottom of her soaked pull-up growing bigger and bigger, almost to the size of a grapefruit. The heavy garment started sagging just as the young tyke finished up her business. Letting out a loud sigh of relief she stood up, her legs pushed apart into an awkward stance by the newfound load between them. She put a paw up to her mouth and sucked her thumb.
"There, there," Lemonade comforted, walking over to his sister and putting an arm around her. "Accidents happen."
"I know," Milk replied matter-of-factly. "I tink gwamma will undewstand." She first looked down at her warm, heavy pull-ups, then up at her big brother. "I just happy I don't gotta go potty no mowe! I feew so much bettew now!" She turned around and waddled back to her bed, climbing back in with a squish. "You should go, too," she said with a yawn as she pulled a sheet up, "I don't tink gwamma will mind if you have an accident, too. Accidents happen!" With that she rolled over and went back to sleep.
Lemonade bit his lip. "Sure, easy for her to say," he muttered, "she's the one with a diaper on." He stood by the door and mulled over his options. 
He could try to finish his trip to the bathroom, but if he didn't want to go down that long, dark hall before, he certainly didn't want to do it now, when he would once again be all by himself. If he didn't do that, though, what could he do? He obviously wasn't going to be able to hold it until the morning, so that meant...could he find somewhere in the room to relieve himself? He quickly searched for anything he could use. Frustratingly, there weren't any spare bottles lying around, nor was there a convenient chamber pot resting under the bed. He could try borrowing one of his sister's pull-ups, but they most likely wouldn't fit him, and regardless, the garment would surely be no match for his much larger bladder. Lemonade started dancing around and whining, his paws clenched to his crotch more tightly than ever. Time was running out!
The little Meowstic's eyes fell on his bed, and he thought about what his sister had said. Yes, accidents happen... and if he peed himself in bed, his grandma would just think he had gone in his sleep: a simple bedwetting accident. Surely she couldn't get mad at him for that, right? It wouldn't be his fault, after all. Having run out of options, the young Pokemon made a dash for his bed and jumped in, hurriedly moving the quilt out of the way before sitting down.
Lemonade had no problem at all relaxing his sphincter; the cat Pokemon's body was all too glad to finally relieve itself after waiting for so long. He moaned in relief as the pee rushed out of him, darkening the front of his pajama pants. A gushing stream of wet warmth flowed from his crotch, soaking his pants and sheets, as well as the mattress beneath him. As the cascade continued he silently apologized to Captain Danger; the Magmar superhero's visage was no doubt going to be stained yellow after this, along with the rest of the Meowstic's white and red briefs.
After a minute or so the flow died down to a trickle, then to a dribble, and finally to a stop. Lemonade sighed with relief, his cheeks completely flushed. Although he had just turned his pajamas and sheets into a warm, pungent river, and he had probably wrecked his grandma's mattress, he did have to agree with his sister: he really did feel much better now that he didn't need to go anymore. A contented smile crept up the little Pokemon's face as he laid back down and pulled the quilt over the mess he had made of the bed. "Besides," he thought as he closed his eyes and slowly started drifting off to sleep, "accidents happen."