An item or person that is generally agreed to be good, but for no particularly specifiable reason, thereby giving off a general aura of genuine 'goodness'.
Having genuine worth (unlike shifty) but achieving it effortlessly (unlike stripper)
Being spongey is an extremely desirable state of existence
Forget about that tart Katrina, she's stripper. Not like Kristine; now there's a spongey chick.
Spent last night round at Jamie's place, had a few beers, watched the footy - it was spongey.
Gees when I first met Kirby I thought she was shifty...but once you get to know her she's actually pretty spongey