Experiment

Oh! Hi Big Mac! Would you mind helping me with an experiment real quick?
Eey-nope! Nopenopenopenopenope
Big Mac! Wait! Huh... why did he run away? I was just--
Horseapples, I grabbed the wrong cooler!
Wow, good thing I caught this now! That would have been embarrassing -- and potentially fatal!

The lab is supposed to be modeled after Twilight's basement (somewhat)
Twilight is wearing the Das Maddendoktor and the Chronoscarf (and Owlowiscious in place of Archimedes) and Big Mac has the Toss-proof Towl.

Art (C)
MLP:FiM (C) Hasbro/Lauren Faust
TF2 (C) Valve