Plot hole: For the past 5 series, Bulk and Skull have been in every episode. They've seen villains from other galaxies (Lord Zedd, Rita Repulsa, The Machine Empire, and Divatox) who have all sent monsters to Angel Grove and threatened Bulk and Skull on countless occasions. They've even been turned into monkeys and made invisible by space creatures. Why do they feel the need to spend Series 6 seeing if alien life exists? Surely 5 series worth of aliens is enough proof?
Plot hole: Quite often the Rangers were contacted at school and would teleport to the command center, danger zone, etc. It is safe to say that the faculty would notice star pupils missing classes so often, yet it was never questioned or addressed.