When the fast movement cheat is on, arrows and boomerangs make much more sparkles than usual.
726: Fast movement = loads of sparkles
Fast movement has always been a somewhat tenuous hack with not entirely sensible effects on game physics. Since it's intended for quest testing purposes only, I'm not entirely sure about the necessity of fixing inconsistencies like this.
besides, you can just hold in ~ or press F1 if you want to move fast since having fast movement on usually means your already invincible.
Fast movement basically makes Link animate 8 times faster. A bunch of stuff is tied to Link's animation - water splashes, grass effects, and, as you've noticed, sparkles. Link animates faster means those things happen faster.
Unexpected, I agree, and in 3.0 random code will hopefully be less tied to other unrelated code, but for now not really a bug.
'Not A Bug' thread moved from quarantined to exterminated. Dark Nation (or other developer), how am I doing? Reply only in one of the threads I moved.