It's from xkcd.com, which is a web comic written by an ex-NASA roboticist. He's just saying plutonium is so ridiculously useful that it's almost like a cheat that shouldn't even exist. The alt text from this particular comic is this:
"Plutonium...
It's like someone briefly joined the team running the universe, introduced their idea for a cool mechanic, then left, and now everyone is stuck pretending that this wildly unbalanced dynamic makes sense."
,
https://m.xkcd.com/2115/
"Plutonium...
It's like someone briefly joined the team running the universe, introduced their idea for a cool mechanic, then left, and now everyone is stuck pretending that this wildly unbalanced dynamic makes sense."
,
https://m.xkcd.com/2115/
But also a bit of radiation.
Also it'll decay.