Having rescued the creatures of Pleistocene South America, the team heads back to just before humans arrive in the Americas to rescue North America's Pleistocene Megafauna. Back at the park, Jack has to help assist the security team with an inspection on the paddocks for the giant theropod carnivores.
- A Day in the Limelight: Much like the previous three episodes did for Leon, Jack, and Adrian (respectively), this episode allows a small degree of extra insight for Alice's character. Also proves as the 'episode' where the readers are all properly introduced to all the prominent members of park security that aren't named Nikolai and Colette.
- Animal Stampede: An entire herd of bison antiquus engages in one of these while being hunted by a pride of American lions. Just like in previous missions, the rescue team uses this as an opportunity for a rescue; and as a result, all but a single elderly male make it through the portal in time.
- Bears Are Bad News: The arctodus featured in this episode prove just as much reason to be concerned as the arctotherium in the previous mission. One in particular ends up giving a smilodon quite a beating over the course of a territorial duel that unfolds between them at the end of the mission.
- Big Damn Heroes: Pulled off several times by the rescue team for the benefit of various animals they rescue this mission.
- Brutal Bird of Prey: The neophrontops are very quick to try to defend a carcass when they see the rescue team nearby, even going so far as to charge towards the team when their attempts at intimidation don't work...just as the team had hoped. The teratornis duo similarly prove more than willing to actively kill the already grievously wounded Eshe the American cheetah so that they won't have to wait for her to die before eating her and are still very aggressive even after they've settled in at the park.
- Canon Foreigner: In this chapter, we are introduced to hoofstock keeper Horace Northup as well as mammal carnivore keeper (and Cass's older sister) Tina Cheng; neither of whom were previously present in Prehistoric Earth. Likewise introduced are the equally newly created security guards John Willowby, Peter Farnsworth, Calum Fox, David Doody, Joe Bristow, and Anita Watts.
- Circling Vultures: A flock of neophrontops are very quick to come descending down upon a Columbian mammoth carcass that had previously been the motivation behind a battle between a six-strong group of American Cheetah and a sleuth of arctodus. A pair of teratornis likewise are eager to come down to attempt to kill and eat an already severely wounded and weak American cheetah. Played with in regard to a flock of Clark's condors, a flock of cathartornis gracilis, and a flock of gymnogyps amplus trapped in (and subsequently rescued from) the La Brea Tar Pits due to the doom being foreshadowed being just as much their own as that of the other animals trapped alongside them. And even after their rescue and integration into the park, the two teratornis prove rather aggressive.
- Curbstomp Battle: Despite managing to put up a very decent fight in the process, Diego the smilodon is ultimately soundly defeated by Smokey the arctodus during their territory duel. And he would have been killed by Smokey as well if not for the timely intervention of Leon.
- Cute Owl: In contrast to the prehistoric vultures, the nine rescued La Brea owls prove quite adorable and friendly.
- Determinator: Diego the smilodon proves very much not one to give up easily over the course of his battle against Smokey.
- Fantastic Fauna Counterpart: As described in Suspiciously Similar Substitute below, a lot of the animals encountered in this mission behave very similarly to animals encountered in the episode immediately before this one.
- Hidden Depths: As much as they all may look more like athletes rather than nerds, all of the security guards Jack gets introduced to in his subplot for this mission have done a lot more research on the matters they need Jack's assistance on than they initially let on.
- Honorable Elephant: The American mastodons and Columbian mammoths prove to be this after (and in the case of all but two of the Columbian mammoths, before) their rescues. Of course, just like with the notiomastodon, the adult males are all kept separate from the females at the park, just in case.
- I Can Still Fight!: Diego the smilodon still continues fighting even after receiving multiple serious wounds over the course of his duel against Smokey the arctodus. He even manages to actively work to start getting back up on his feet after getting blown across the grassland by a swing of Smokey's paw and sent pounding against the side of a large tree. And it isn't until Smokey manages to charge into position in time to smack Diego back down to the ground before the cat can finish getting back up on his feet that Diego is finally defeated and at the bear's mercy.
- Interspecies Friendship: One of these (by a certain definition of 'friendship') is revealed to have formed between Dermot the doedicurus and the hoofstock keeper Horace Northup.
- It Can Think: A valid concern that the Prehistoric Park security team prove to have over the allosaurus, as they all know the potential dangers of having such creatures turn out to be a 'cage breaker'.
- King of Beasts: The American lions are animals that Leon proves visibly in awe at seeing, are implied to serve as Always a Bigger Fish by the way the teratornis and Eshe the American cheetah react to the sound of their roars, and prove equal parts fearsome and majestic by virtue of the vicious hunt the females engage in against a herd of bison antiquus and the resident alpha male being described as confidently strutting his way over to the subsequent carcass the pride gets for a meal when its time for him to get first bite.
- Let's Split Up, Gang!: Another case of this occurs during this mission. This time Leon and Drew head off together in one direction while Alice heads in another direction on her own.
- Made of Iron: Diego noticeably takes quite a beating from Smokey prior to his defeat. And it's even entirely possible that he would have still managed to successfully get back on his feet after getting sent flying and pounding against the side of a large tree if it hadn't been for Smokey charging over in time to smack him back down before he'd finished getting back up.
- Mighty Roar: Played straight multiple times between Diego the smilodon and Smokey the arctodus. Even the female smilodon Shira lets off one of these at the very end of the chapter.
- Gets weaponized by Leon via use of prerecorded roars on a specially designed 'broadcasting device' that he starts using to attract animals into coming through the portal.
- Alice herself ends up briefly taking a page out of Leon's book by using a recorded lion roar from a backup device Leon allowed her to borrow during their case of Let's Split Up, Gang!. As a result, she is able to scare off a pair of teratornis into going through the portal before they can kill and eat a severely wounded adult female American cheetah.
- Named After Somebody Famous: Nero the dire wolf is named after the famed Roman emperor.
- Noble Bird of Prey: Averted with the prehistoric eagles and caracaras rescued in this mission. Understandable considering they were helpless victims of the La Brea Tar Pits at the time of their introduction and would have died if not for the timely intervention of the rescue team and various other staff members brought along to help them get out.
- Noble Wolf: Nero and his entire pack of dire wolves prove to be this when their not hunting or struggling for their lives in a tar pit.
- Panthera Awesome: Smilodon fatalis, homotherium, American cheetahs, and American lions are amongst the animals rescued in this mission. And the two bachelor smilodon populator brothers, Raul and Carlos, are observed by Tina Cheng back at the park.
- Pesky Pigeons: Averted by the flock of passenger pigeons that get rescued by the gang over the course of the mission.
- Quicksand Sucks: A massive number of animals end up trapped in (and subsequently rescued from) the La Brea Tar Pits.
- Savage Wolves: A rescued pack of dire wolves prove quite vicious in their desperate attempts at struggling to free themselves from the tar pits before they finally get rescued.
- Scavengers Are Scum: While mostly averted, the teratornis duo rescued quite noticeably receive elements of such a portrayal in that they appear very eager to try to finish off an already grievously wounded Eshe the American cheetah instead of patiently waiting for her to die from her wounds.
- Shout-Out: One of the male megatherium from the previous mission is revealed to be named Sidnote , and his mate is
confirmed by A-LionGleek to be named Camillenote . Similarly, the two smilodon fatalis rescued in this mission are named Diego and Shira, a single male arctodus that Diego does battle with is named after Smokey the bear, the male amongst the American lion pride is named Lafcadio, and the Columbian mammoth matriarch and the adult male she mates with are named Celeste and Babar. - Shown Their Work: The vocalizations of the California tapirs are actual vocalizations made by real life modern-day tapirs (even making the correct noises within specific contexts that they do so in real life).
- Speaks Fluent Animal: Well maybe not quite 'fluent', but Leon does manage to make good progress in rescuing the animals through use of both various animal vocalizations prerecorded on a specially designed 'broadcasting device' as well as a very brief instance of vocally imitating a smilodon snarl with his own voice.
- Spiritual Antithesis: To the previous episode - that one focused on the weird megafauna in South America, this one focuses on the more familiar ones from North America. Even the greatest challenges that crew face are opposites - the previous episode had numerous animals running from a fast moving bushfire, while this one has the team pull several animals out of an immobile tar-pit, which will kill them far more gradually than flames ever could.
- Suspiciously Similar Substitute: Many animals from this 'episode' fill similar roles to ones found in the previous one, "Red In Tooth And Claw". Justified by the fact that this episode and the former occur after the Great American Interchange, where wildlife on both continents migrated to the other, to varying degrees of success.
- Took a Level in Badass: Leon shows signs of slowly starting this by virtue of his broadcasting device.
- Those Wily Coyotes: Averted with the Pleistocene coyotes, as they are too busy first struggling to get free from the La Brea Tar Pits, then whimpering and barely conscious immediately following their rescue, and then happily eating sheep carcasses in their new enclosure home at the park to take part in any stereotypically wily behavior.
- This Is Gonna Suck: Leon and Alice's reaction upon realizing that they'll have to go toward the foul smell emanating from the La Brea tar pits.
- Vile Vulture: A flock of neophrontops encountered by the rescue team prove quite eager to defend their carcass from what they believe to be would-be thieves. Likewise, the teratornis duo rescued prove not only perfectly happy to attempt to finish off an already grievously wounded Eshe the American cheetah so they won't have to wait too long before they can eat her corpse but also remain highly aggressive even after they've been sent to the park and placed in their new exhibit.
