In which Penelope makes an uncalculated – and incalculable – error.

↓ Transcript
Panel 1:
(Back in the rafters, Penny starts up her buzz-saw.)
Johnny: Penny, are you sure that’s a good idea?

Panel 2:
(She attempts to cut into the gas canister.)
Johnny: You don’t even know what that stuff is!
Penny: Oh, I’m quite sure.

Panel 3:
(Penny pauses in disbelief.)
Penny: Huh! Nary a scratch! I wonder -

Panel 4:
(The gas canister explodes in a huge mushroom cloud.)
SFX: WHA-BOOOM!