Sprincess Pielight Tarkle... or Princess Twilight Sparkle (once the script was wiped clean) may have collected a bit of Smooze goo after the Gala. She might have been researching it. She also possibly spilled a little while running an experiment on its properties.
There would be only two potential issues with this, highly theoretical, and by no means representative, situation: 1... it's from a highly magical, elder beast, and 2... it's immune to conventional magic.

Things could potentially escalate.

<Spike facepalms and writes a letter>
Okay. Things escalated quickly.