I don't see where you're getting at...
Critters are in slow evolving process into Twomphs from Super Mario 64! Power Critters are blue and heavier than a normal critter. In just a few generations, they all will become twomphs, the supreme type of spike-protected entities!
{Actually, it'd have to be tougher than metal, seeing as how Quote's made of metal, and still dies}
There's no proof that Quote is made of metal, is it? He could be made of e.g. plastic substances, or perhaps wood? Wait, not wood, since he doesn't float.... And, um, could a piece of metal jump four times his own length straight upwards? Perhaps if Quote is half metal, half balloon, the spikes' danger would be more logical.
Oh, also, stone in general is tougher than metal in general (drills excluded, but Quote isn't a drill ^_^), so if critters are made of stone, they'dn't get too damaged from spikes, right?
And we're missing a very important detail here -
XP Crystals are immune to spikes!! How terrible! The triangles of doom! - - -actually, it's quite fun. Sorry for missing your point, VoidMage_Lowell, but I see it now. ^_^ It would be pretty fun with a <is it called
lampshade?> scene where Quote ironize over that.