Jazz enjoyed and took advantage of any excuse for a party, and the  father of two of their new friends being rescued from an eternity of  non-existence was definitely a reason for a party. He talked to  Sideswipe and Sunstreaker, and confirmed that their next brew of  high-grade was just about ready, talked to Prowl and confirmed that it  was unlikely that the Decepticons would attack within the next week (not  to mention he was debating inviting some Decepticons - they did play a  part in Gaster's rescue, after all.), talked to Optimus and confirmed he  was okay with it and after that business was taken care of, got to  work.

As for the monsters' participation in party  planning, Toriel took it upon herself to prepare nearly all food  involved. In the space of a few hours, she had cooked up a truly  astounding number of pies, including some of, quite frankly, sheerly  intimidating size for the larger and more mechanical partygoers. It was,  after all, Magic food, so it was assumed that it would be fine for  mechs to eat.

Decorations were put up in the commissary -  nothing special, just the usual party things; lights, sparkly things  (Undyne tried to insist that the decorations needed more spears, but her  requests were declined each time), an Autobot sized disco ball that  someone had snuck in one party as a joke, then had continued to be used.  Tables were moved to make a dance floor, the DJ booth was erected, and  the whole of what usually looked like a lunch room turned into a  club-themed party room.

Prowl and Optimus even okayed  Jazz inviting the Decepticons. Red Alert had a few things to say about  it, but nevertheless, was overturned. Gaster wanted to see his friend  Skywarp, anyways, and this was his party after all.

So,  about half an hour local time before the party was set to begin, the  Decepticons arrived. Only a few came - Megatron, Soundwave, Starscream,  Thundercracker, Skywarp. Gaster, Jazz, Prowl, and Optimus were waiting  for them at the entryway to the Arc.

Gaster's gaze  latched immediately into the Decepticon leader. "I don't recall sending  you an invite." His voice was calm, but his expression said something  more akin to "get out now before I murder your face off."

Megatron  sneered. "The invitation was open to all Decepticons who would remain  peaceful. I remember the parties Jazz used to throw. I will not be left out. And I've heard rumors about the Twins' high-grade."

Jazz snickered quietly behind his raised hand.

Gaster nearly made a remark about how not only was this his party, but he was also the Dog-blasted Royal Scientist, for crying out loud, and if he didn't want Megatron there, then Megatron had better leave, but the invitation had  been an open invite, and Gaster supposed turning the mech out might not  leave the greatest impression on his new Autobot allies. So he just  gave Megatron an I'm-watching-you gesture then shrugged.

Optimus  Prime stepped forward. "Megatron. It is... good to see you not on the  other side of a weapon. Starscream, Soundwave, Thundercracker,  Skywarp... I appreciate your trust in us."

Starscream  snorted, and Skywarp giggled. "We just wanted to see Gaster again. I  spent a long time with him," the purple Seeker said. "How've you been,  by the way?"

Gaster grinned. "Well, I exist again, so just  about anything that happens is a definite improvement over my previous  state. So, pretty good!"

"Awesome!" the warper exclaimed with a grin.

"Hey, mechs," Jazz interrupted, "The party's ready to go and everyone else is already there... let's party!"

Optimus stepped aside and gestured the Decepticons into the Arc.  Prowl led the way to the commissary, where the normal lights were off  and the flashing, multicolored party lights were already sparkling.  Music was just beginning to play as Blaster, accompanied by a ghost  monster, fiddled with technical equipment in the DJ booth. Monster food  and energon were laid out on a massive table near the door.

Mechs  paused to look as the massive Decepticon Warlord entered the room  followed by the others, but they had already been alerted to his  arrival. It unnerved a few mechs, but who were they to argue? The mech  had promised to remain peaceful, and as long as he did, they had no  reason to be too scared. Besides, the Autobots (and monsters) vastly outnumbered the Decepticons.

Megatron  immediately turned to the refreshments table and picked up a cube of  the most potent high-grade there was, and downed a quick gulp.

Then he coughed. Sunstreaker and Sideswipe exchanged a high-five.

After  seeing Megatron choke on the potent energon, Gaster grinned rather  viciously and picked up a (monster sized) cube of his own. He had had  energon since existing again, but had not yet had the opportunity to try  any high-grade. He got it down with considerably more success, a look  of appreciation crossing his face. "Not bad."

Megatron grinned and took another gulp. "Indeed, for earth energon. You should have tried the stuff we had on Cybertron!"

Skywarp  sneaked a cube from the table and took a sip, and made a face. "Here,"  he said, and shoved the cube to his Trine leader. "Why are there giant  pies?" he asked after a moment of examining his other choices on the  table.

Gaster pointed in the direction of a number of  large dishes, then added, "All of them are excellent, but I especially  recommend the butterscotch-cinnamon, or the snail pie. Trust me, it's  much better than it sounds." Then he took another gulp of energon and  addressed Megatron. "Of course, I used to make a rather astonishing home  brew when I lived in the Rockies..."

As the two continued  to bicker about who had experienced the beverage with the most kick, on  seeing Skywarp approach, Toriel gestured to her many culinary creations.  "Please, allow me to get you some pie. What kind would you like?"

"Um, could I try some of that one?" Skywarp pointed to the largest of the bunch. "What kind is it?"

"Raspberry and blueberry mix," Toriel replied, smiling, as she reached for the pie knife."

"Oooh... I've heard of those. Aren't they human food? Is it safe for me to eat?"

"Of  course! When a monster cooks, much of the food's physical matter is  replaced with Magic! If it weren't, I'm not sure that many monsters  would be able to eat. After all, many of them don't even have stomachs!"

Wheeljack  sidled over. "And, we've discovered, Magic and energon seem to work on  similar principles. We can gain energy from monster food, and monsters  can get energy from energon. It's not as efficient, sure, but it works."

Starscream was eyeing the massive display of human(looking) food. "Really."

Wheeljack nodded. "Really really. Ratchet even okayed it."

Having cut out a sizeable slice of pie, Toriel offered Skywarp the plate, smile widening a little. "Go ahead, try it!"

The  purple Seeker picked up the mech-sized fork awkwardly (most of their  food did not require any use of utensils) and clumsily, though  carefully, took a bite. He closed his eyes and tasted. "Huh. That's  awesome. Tastes like those crystal candies you used to get me, TC."

Thundercracker eyed the plate. "Can I try?"

Skywarp fed him a bite.

"Hm. That's pretty good. What other kinds do you have?"

Before  Toriel could answer, there was a crash nearby as Megatron stumbled and  fell over. Not an instant later, a loud, raucous laughter tore through  the room. "HA!" Gaster laughed, jabbing a finger in Megatron's direction. "You thought you could out-drink me?! Well, guess again, you Dog-blasted Decepticon, I'm the Royal Scientist!! You can't drink more than me!"

Optimus  Prime stepped up next to the massive mech and clapped his hand on his  shoulder. "Come, Megatron, this is not a competition. Have fun. Let us  put the war behind us. I do not know if the monsters can even get  overcharged on high-grade like we can. In any case, cheers. To a good  year, and the return of loved ones."

Somehow, the little  private comment was heard by all (a talent of being Prime, perhaps), and  the whole room cheered and those who had cubes or glasses of things to  drink lifted them.

As the night wore on, a good time was  had by all. It turned out monsters could get overcharged, as Gaster  accepted all challengers in a drinking competition, and while he himself  remained quite sober, Undyne became thoroughly drunk and eventually  Alphys had to lead her away from the party, as she had been screaming  about fighting anyone and everyone with her hands tied behind her back.

Megatron  and Optimus Prime ended up sitting opposite each other at a small  table, talking about old times and peace. Starscream, Skywarp, and  Thundercracker, after trying a piece of every one of Toriel's pies (and  agreeing that every one was delicious), spread out across the room.  Starscream got caught up in a discussion about energon and monster food  with Toriel and Wheeljack, Skywarp started talking to Sans about warping  and shortcuts, and Thundercracker got caught up in a conversation with  Alphys about a particular form of human literature that no one else  really knew anything about (Alphys seemed unnaturally enthusiastic,  talking about some... kissy cat thing?). Soundwave slowly made his way  over to the DJ booth and sidled his way up next to Blaster and the ghost  monster, Napstablook, and added a few selections of old, old, pre-war  Cybertronian music to the que.

Eventually, well beyond  midnight, things began to taper down. After giving Thundercracker her  phone number, Alphys said she had to go check on Undyne, and Sans  eventually collapsed in Gaster's lap, either drunk, exhausted, or some  combination of the two. Gaster, for his part, was still completely fine  despite having out-drunk a number of monsters and mechs, and took both  his sons to get them to bed (he acted like they were still rather young  children).

Megatron was passed out in the chair he had  been sitting in while conversing with Optimus, head rested on his folded  arms. Optimus had left shortly after the Decepticon Warlord had fallen  into recharge, instead picking up a conversation with Asgore, who had  arrived a little late to the party. Prowl had snuck out early on, as he  didn't enjoy high-grade or loud noises, nodding to Soundwave in the DJ  booth and Starscream still talking to Toriel and Wheeljack. Jazz flitted  about the whole night, energy seeming to never drop below 100%. Until  Gaster had collected Papyrus to head home, the youngest of the skeletons  had quickly become friends with Skywarp, and the two had exchanged  numbers and promised to have a family gathering soon, the Trine and the  three skeletons.

Sideswipe and Sunstreaker had attended  the refreshment table and kept the high-grade well stocked, and were  some of the last to be still there and awake as Blaster and Soundwave  and Napstablook started toning the music down and winding things up.

Optimus  Prime approached the Decepticons and told them that if they preferred,  they would be allowed to stay the night in the commissary, as long as  they continued to observe the peace rule. As all were at least slightly  overcharged, they agreed it wouldn't hurt anything to sleep off the  charge in the Autobot ship.

Overall, everyone pretty much agreed that the party was a massive success.

§

A/N

Another one of these!