Eugene inflates a balloon in the science lab using a tap labeled VAC (vacuum).
When Ned is cleaning the mess left by Chuck and Olive in the Bitter Sweets candy shop (i.e. the release of rats), he uses his Digby-petting device. When he goes to retrieve the rat from the vat with pink goo, there is already a prominent amount of goo (albeit dried) on the lower half of the arm/hand.
When young Ned jumps in the pile of dead leaves, the ones he touches become "alive" and green again. A leaf is dead the instant it detaches from the living tree it was once a part of, even if it is still green for a time, so touching a dead leaf would not bring it back to "life". Further, if this were cannon for Ned, everything that was ever part of a larger living organism that Ned touched would spring back to it's texture and state it bore when previously part of the whole: leather, meat in food items, literally anything that was once part of a living thing.