Awesome / Undertale the Musical

• When Finale kicks in after Your Best Nightmare. The souls who have been used in Flowey's violence are incredibly pissed and, after offering to keep Frisk company, swear to fight Flowey and taunt him as he has his villainous breakdown:
  Souls: Blow after blow/Your HP will lower/ Now dance to OUR puppet strings!
• Hopes And Dreams. The ending of the song implies that Frisk somehow found a way to save Asriel.
• The creators get one for this whole project. Especially given the final version is an over four hours long epic.
• "Power of NEO" was already considered to be one of the best songs of the Genocide Package, but there's a blink-and-you-miss-it Moment of Awesome in one of the text boxes for the full Mettaton NEO 2.0 battle they used; "You notice a damp patch on your arm. There is a red puddle on the floor." If there was any question as to whether or not Mettaton NEO was still just showboating to buy time like in the game proper, this makes it clear that, while he acknowledges he's not likely to win, he's going out swinging and with full intent to save the day this time around.
• Easy to miss, but if you look closely near the end of "Megalovania", you'll notice that Frisk makes it to Sans's unavoidable but non-lethal "slam your soul against the wall" attack with 2 HP left; basically, if they had brushed up against that Gaster Blaster ring once more, they'd have lost.
  • Stelyos' voice acting. As he acknowledged in a comment, he could have sung perfectly, but instead deliberately jumped whole octaves at the drop of a hat to portray the sheer rage and sorrow Sans is feeling when you fight him.
• A week after the Genocide package ended, a new video was put up, with a character nobody expected: the man who speaks in hands, W.D. Gaster himself. Cue the sounds of the audience losing its collective shit. Not to mention how the video ends; with Gaster killing the Fallen Child. Consider this song takes place after the Genocide Package^note  The Fallen Child uses the Real Knife and Gaster mentions his "fallen sons", and Sans only dies on that route. and it shows why you should beware the doctor who speaks in hands. And what he says after doing so — in a suitably-ironic way by forcing them to stab themself through the SOUL with their own Real Knife via a dimensional rift in front of himself, no less — implies he's making it stick.
  Gaster: Such determination — if only I had some when it mattered. Ah, well. That's fate, I suppose. Now, then; time to change ours. Shhh... do you hear that? (a faint silhouette of the smiling Gaster can be seen dragging the fatally-wounded Fallen Child into a pitch-black abyss) That's the call of the void.