2008-05-01
If Pili-Pala is already untapped, you can't activate its {Q} ability. That's because you can't pay the "Untap this permanent" cost.
2008-05-01
If a creature with an {Q} ability hasn't been under your control since your most recent turn began, you can't activate that ability, unless the creature has haste.
2008-05-01
Pili-Pala's ability is a mana ability. It doesn't use the stack and can't be responded to.
2008-05-01
Using this creature's ability means you're untapping it for mana, not tapping it for mana. Mana Reflection won't cause it to produce extra mana.