So who put the grumpy juice in Randy Jackson's Coca Cola cup?

I ask because judge Jackson seemed intent on dinging the early performers on Tuesday's American Idol, regardless of how well they actually sang -- criticizing Michael Johns, Syesha Mercado and Kristy Lee Cook after they gave some of the best performances of the night.

This week's performances -- already a bit topsy turvy because of the Idol Gives Back charity extravaganza airing tonight -- was seriously skewed tonight as one-time front runners David Cook and Carly Smithson faltered under the weight of some seriously questionable song choices (stung by allegations he's taking credit for obscure rockified arrangements of well-known hits, Cook instead chose an Our Lady Peace song sure to confuse Idol's teenybopper voters)

It felt a bit like Bizarro Idol Tuesday, as singers like Jason Castro and Kristy Lee Cook. who seemed poised for ejection just a few weeks ago, delivered some of their best performances in recent memory. Johns keeps working the hunk factor for all it's worth, taking serious props for essentially regurgitating popular rock songs. Who knows what kind of artist he might turn out to be if he actually wins this thing -- he looks good in tight pants and can hit all the notes on some challenging classics.

David Cook, Smithson and Brooke White all have the same problem; they peaked a bit early and are each struggling to deal with the mounting pressure. Here is the hidden factor that shapes the Idol contest: whether contestants can handle the strain. Shows like Idol love performers who flower before the camera's eye; falling to pieces under the pressure, as an increasingly frazzled White seems to be doing each week, isn't nearly as appealing.

Strange as it sounds, those are also the three singers most in danger of leaving this week. Idol often has a surprise ejection midway through the competition, and these three wound up offering the least impressive performances on a show where nearly everyone else raised their game.