Obligatory Disclaimer: The TMNT, Master Splinter, April O'Neill, Casey Jones, Angel, Leatherhead, Professor Honeycutt and Klunk do not belong to me, they all belong to Laird and Eastman, and Mirage Studios.

Important Author's Notes: This fic was inspired by a challenge on the Stealthy Stories forum. It takes place in the second half of the fourth season, after Leo comes home from Japan and Bishop's alien virus starts screwing up the city's bug life. However, the Good Genes arc doesn't happen in this fic – in a sense it's a replacement for that arc. I kind of need it to be that way.

Also, this fic deals with something that I don't think many people tackle much in fanfics in any fandom. We've all seen fics in most fandoms about characters being addicted to substances like alcohol or illicit drugs. But what if it were something much more mundane and everyday? What if it were something you thought was perfectly harmless and used all the time? What if you weren't in denial of an addiction, but rather didn't even realise a problem could be possible?

-- "I've been worried a lot lately… Master Splinter tells me that I worry too much. Okay, you tell me. Should I be worried?" – Donatello, Scion of the Shredder (Season 4 Episode 15)

APPLIANCE.

There were still several hours left before the sun was due to rise, and already it looked like it was going to be a very, very long day.

"Do you HAVE to be so difficult?" Donatello hissed in exasperation, keeping his voice down in deference to the horrifically early hour and the rest of his family who were clearly saner than he was, since they were all asleep. He didn't receive an answer from his antagonist, not did he expect one. Gritting his teeth and mentally cursing manufacturers that made caps that were not only child-proof but apparently ninja-proof and turtle-proof as well, he finally wrestled the aspirin bottle open and quickly shook a couple of tablets into his hand. Recapping the bottle and replacing it in the cupboard as quickly and quietly as he could, he swallowed the aspirin with a mouthful of cold coffee, grimacing as his stomach protested. He stared at the silent, still and now empty coffee maker balefully. Still, it'll have to do for now. I can't start a new pot just yet or it'll be cold by the time the guys get up, then I'll have to make another one again. Cold coffee is better than no coffee, I guess. Besides, there's far too much to do. I need to finish that program for the security systems before I can even think of catching a nap before early morning practice…

Taking his mug of cold wake-up juice back into his lab, he set the cup down and absently rubbed at his sore leg where the sliced flesh continued to throb and ache. Briefly wondering why it still hadn't started to heal yet, Don glanced at his computer and promptly forgot all about his leg, his headache, his coffee, and just about everything else. Oh no, no no no, I am NOT seeing this!

He'd grown accustomed to Klunk's company whenever he pulled an all-nighter. Truth be told, he rather liked it. There was something strangely comforting about the soft purring as Mikey's beloved cat curled up on the computer tower and watched him drowsily with curious golden eyes. Unfortunately, Klunk had occasionally expressed interest in Don's racing hands as they rapidly typed, flying over the keyboard. He'd even occasionally swatted at the green hand playfully. Don had never minded – after all, Klunk was just interpreting things from a cat's point of view, and it must have seemed as though Donatello was spending many nights toying with some very strange type of prey. Don had usually found that gently but firmly lifting the bundle of soft fur back onto the warm, whirring computer tower usually settled him right back down. However, this time Klunk had obviously taken advantage of Don's absence to create his own rendition of "Kitten On The Keyboard".

Right in the middle of some very intricate reprogramming for the vitally important security systems.

"Klunk!" Springing forward, he snatched the frolicking feline off his precious keyboard, ignoring the squawk of protest from the cat as he stared in dismay at the monitor, which showed that several hours of work had been transformed into barely-salvageable gibberish. Barely.

Turning his attention to the squirming cat in his hands, Donnie's furious glare faded as he realised that Klunk was frantically digging claws into his hands, squirming, trying to get out of his grip. A grip that was far too tight, and squeezing Klunk too hard.

"Oh shell! Klunk, I'm so sorry!" Quickly setting Klunk down, he watched as the family feline scrambled away from him into the safety of the lair without even pausing to straighten his ruffled fur. Don winced, rubbing his hands where Klunk's claws had scratched him in an effort to loosen his grasp. I… I nearly hurt Klunk. What if I HAD hurt him? Mikey would never forgive me. I'm not sure I could forgive myself. What sort of monster hurts a helpless cat over something so small? Well… Okay. Maybe not quite so small. Rather big, actually. He stared at the monitor, which cheerfully mocked him from its position on the desk, before sighing and thumping his head against the wall.

THUD. THUD. THUD.

So much for fixing my headache. Oh well, it can keep my leg company. And my stomach. Ow. Rubbing at his plastron above his pained stomach, he wondered why he seemed to get an upset stomach so often nowadays.Shaking his head, he sighed. He had more important things to worry about than that. Estimating how long this mess would take to repair, for example. No way will this be finished by early morning practice. And it's all my own fault – I know better than to leave the computer without saving my work.

Making a mental note to put aspirin on the shopping list – again – Don began the long process of reading over the entire program, checking each line carefully for cat-induced errors.

Yes. This was going to be a very, very long day.

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It was Splinter's habit to awaken early in the morning before his sons. In fact, until recently only very unusual circumstances would cause him to awaken to any sounds other than the soft snores and sighs of his four boys. In the last year, however, other habits had developed, and Splinter's ears flicked as he assessed the sounds of his home in the pre-dawn hours. Two sets of not-so-soft snores made him smile softly – Raphael and Michaelangelo. They slept as they did everything else – whole-heartedly and energetically. They had been the restless sleepers as children – he had long lost track of the amount of times Leonardo or Donatello had come to him complaining that Raphael was kicking them in his sleep, or that Michaelangelo had stolen the blankets. Ah, kids.

Of course, this had probably encouraged the other two in their habits. Donatello had always been the last to fall asleep and the first to awaken as a child, as his curiosity to learn of the world around him was without end, even though his life in the sewers had not been so fortunate or limitless. And Leonardo had also preferred to wake up early, though he had not been the night owl Donatello had been. Instead, he had learned early of the value of peace that could be enjoyed prior to the awakening of his brothers.

Speaking of his early-bird students… He was not surprised to hear the sounds of warm-up katas being performed in the dojo. For a worryingly long time, this had been an everyday occurance to wake up to, as Leonardo battled constantly against an imaginary opponent while ignoring the true antagonist deep inside. Thankfully, with the help of the Ancient One, he had finally faced this inner battle, and won. But Leonardo was still the son that was most devoted to ninjutsu, as he always had been, and he often chose to begin the day by waking early and spending a short time in solitary practice. That is fine, my son, if you so wish it. As long as you do not forget again that solitary is not how your life was intended to be. Your brothers and I are watching you, and we shall not allow you to forget.

And speaking of brothers… yes, Splinter could hear the telltale clickity-clackity sound of Donatello typing at full speed. He frowned. I do hope he has not been awake all night again. A hobby is quite fine, and I will not deny that his technological abilities have made our home safer and more comfortable in a considerably short period of time, but he is neither properly focussed on the lesson, nor capable during sparring practice after these sleepless nights. Pondering the matter, Splinter finally decided to let the issue be for now. If there is no improvement, I shall talk to him later. But Donatello is observant, and I imagine a few morning sessions at the wrong end of his brothers' blows will remind him quickly to go to sleep at a more reasonable hour. Plus, I must take his injured leg into account – although he appears to be quite comfortable in placing weight on it now.

Decision made, Splinter rose and began preparations for the morning ahead. After all, there was much to be done.

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A/N – what did you think? Please review. This is only the prologue – there's plenty more yet to go.