Had Gilligan really eaten that many bananas, it would have had disastrous effects on his digestive system.
When Mary Ann hands the pie to Gilligan, it's in a pie pan. After Gilligan attempts to place the pie on the edge of the bathtub, it falls, landing upside-down, and there is no pan, just broken crust.
The professor says that there are seven species of "mantis conti", and that each species has several genera and each genera has several sub-genera. This has it backwards. In biology, species are not divided into genera; genera are divided into sub-genera, and sub-genera are divided into species.