* The death of the mother ''TyrannosaurusRex''. Even Nigel seemed shaken by that.
** Just before she died, the mother Rex let out one last defiant roar at Nigel, probably as a last-ditch attempt to protect her babies.
* Nigel and the popular big cat expert Saba Douglas-Hamilton mourning for sabretooth cats which suffer hunger and finally die because of starvation. And also the sad story of Martha the mammoth and her sister, even though it ends happily this time.
** [[FridgeLogic They could travel through time, yet they couldn't arrive in time to save these animals?]]
*** It looked like they were taking the animals from the times they were becoming extinct to not have as big an effect on the timeline... maybe.
* During the episode "Saving the Sabretooth", the mother ''Ornithomimus'' rejects two of her eggs. Their retrieved and Bob tries to hatch them in an incubator. Soon all the other eggs hatch, but the two in the incubator don't, [[spoiler: thankfully they do hatch eventually]].