The Voodoo Shark entry on the main page states confusion that the principal didn't see a metal spike in the welding mask. However, before we see him don it, we see a pair of hands handling the mask and pressing a hidden switch which deployed the spike. This switch is near the spike, and would likely be tripped when the mask is put on. While the scene cuts to the principal donning the mask after looking inside it, it's quite possible that the hidden switch was tripped by someone else - that, or he had been deceived in some way.
In one episode, Kaede experiences nausea brought on by what she believes to be motion sickness. This confuses Akamatsu, since there have been modifications done to the vehicle, they're travelling in that should have made motion sickness impossible. The following episode, it's revealed Kaede is pregnant. So, she very well could have been experiencing morning sickness rather than motion sickness.
