Professor Z, Corrine and others in “Unfinished Business”

I don't want to alarm anyone unduly, but first the model was helium and Marshall was floating, correct? And now the model has become oxygen - and so has Marshall.

And if Marshall's moving from helium to oxygen, he's moving up the periodic table.

[to Marshall] Hey, maybe somewhere along the way, you'll turn into platinum. They gotta let you into the band if you become platinum.

Lucas, at the rate Marshall's going, he could end up here - uranium.