- In a meta way, the entire premise of the show. Who ever thought that anime could be so educational, or high-school cellular biology be discussed in a way easy for manga fans to grasp? The massive positive reception the series got from professors, medical students, or simply biology enthusiasts is proof of Cells at Work! being Edutainment done right.
- The intro with NK Cell. She slashes apart attacking germs without even looking!
- Episode 3 has Dendritic Cell giving Naive T Cell a heart-to-heart (nucleus-to-nucleus?) pep talk, after which he morphs into the big, muscular Effector T Cell and lays the smackdown on the zombified virus cells!
- Also from Episode 3, the pretty, cheerful Macrophage killing an entire horde of Influenza zombies with a single stroke of her massive butcher knife! With barely any effort at all, mind you, and she's happily smiling and giggling the whole time, with the friendliest sing-song voice possible.
- In episode 4, Eosinophil killing the giant, kaiju-like Anisakis worm with a single strike from her harpoon!
- Earlier in the same episode, White Blood Cell is able to successfully pull an Eat Me move on the leader Vibrio bacteria, which, while not as big as the Anisakis, is still many times his size. He rips it apart from the inside out, then bursts out of its mouth covered in cytoplasm, which, being depicted in-universe as looking like actual blood, is a very gory sight to see indeed.
- White Blood Cell has many, for that matter, but his biggest show of awesomeness to date might just be his first: In a flashback in episode 6 we see that, as a tiny Myelocyte armed with only a rubber training knife, he stood up to a bacterium that was tormenting, and prepared, to kill Red Blood Cell and bought the two of them enough time for help to arrive. The bacterium even offered to spare his life if he'd give up the girl, and he didn't even think twice before refusing. From the start, he lived up to his role as the body's natural-born protector!
- Pretty much NK Cell, the katana-wielding Action Girl. She is known to clash with Killer T frequently, and in a one-on-one fight, easily outmatches him! And if you think she's tough against her allies whom she bickers with, just imagine what would happen if she and any Macrophage partner up.
- Surprisingly, the Platelets themselves, when they charge right into a battleground to repair the scrape wound. The Neutrophils back them up and defend them against the germs. And are they fazed or frightened in any way? Nope, they happily run through and thank the Neutrophils for their help in the cheeriest voices imaginable! These are the equivalents of middle-schoolers running into a literal war zone, mind you.
- In Episode 7, the final battle against Cancer Cell. All the immune cells are there: hordes of Macrophages and Killer T Cells and even Eosinophil and Basophil join in the fray, slashing and stabbing and blasting their way against the gruesome tumor clones that Cancer Cell produces!
Macrophage: My my, I was aiming for his head, but I missed.
- Giving Red Blood Cell some credit, she actively figures out something is drastically wrong with the body demanding immense amounts of nutrients and resources for no apparent reason, and alerts the Immune Cells. A far cry from her usual freakouts!
- Cancer Cell sprouts a pair of grisly-looking flesh wings as he prepares to take down the three immune cells...cue a very well-aimed toss of a cleaver from Macrophage, which slices one wing almost off!
- NK being activated by laughter, with her shining with a colorful aura as she's filled with an extra boost of power to finish off Cancer Cell, who she cleaves nearly in half!
- Cancer Cell himself, in a way, being portrayed as a legitimately threatening antagonist with a terrifying appearance, as well as a meaningful and sympathetic motivation. He is a rare example of a Tragic Villain done right: his motivations genuinely make you feel bad for him, but at the same time, it doesn't gloss over his crimes and evil deeds, and he is justifiably killed off for the body's sake.
- Episode 8; White Blood Cell spends his day carefully helping Red Blood Cell complete her routine without directly seeking assistance (a CMOA of it's own, given the possibility she is a Sickle Cell), and details why to the Killer T Cell, who promptly chews him out and punches him over it, insisting he not associate with non-Immune Cells and retain his killer edge. White Blood Cell goes on to ask Red Blood Cell about her day anyway and happily listens... While Killer T fumes about how he's not envious after seeing other cells interacting.
- Neutrophil's guardian angel act in Episode 8 includes him sneaking up on two Streptococcus and killing them, all so quietly and quickly that Red Blood Cell doesn't even notice! Dude's played his ninja game seriously, stealthily following to guide Red Blood Cell.
- In Chapter 15/Episode 10, Macrophage/Monocytes' Big Damn Hero moment.
- Also from episode 10, the all-out battle between the Staphylococcus horde and the Macrophages, in a full-scale battle between two teams of ladies in puffy dresses! (it's a lot more epic than that sounds, really.)
- Chapters 17 and 18/episodes 12 and 13 feature the hypovolemic shock... And how the cells reacted to the Darkest Hour of the series:
- Due to the enormous blood loss, many germs decide to try and take over the body now that the immune system is weakened. We know that from a pseudomas that was bragging about that before being cut down by U-1146... That then proceeded to slaughter his companions alongside the other neutrophils.
- As the red cells start realizing the situation, the Kohai Red Cell starts losing her nerve... And then AE3803, of all people, reminds her they have a job to do and cells to bring oxygen and nutrients to right now and they don't have time to waste thinking about their numbers having been thinned.
- The platelets successfully sealing the life-threatening wound and stopping the blood loss.
- When her kohai starts having a breakdown as the situation caused by the blood loss is getting critical, AE3803 reminds her their mission and Brightslaps her back into moving. Even in the face of the raging blizzard caused by the cooling body temperature.
- Still, no matter what they do, too many red cells were lost before the platelets could seal the wound... Then, a strange red blood cells from out of nowhere asks what's happening and, upon being informed, he and his army of companions proceed to join forces with the remaining local red blood cells to deliver the oxygen, saving the body.
- This gets better when, once the body is safe, their identity is revealed: they arrived from a blood transfusion... That, from their point of view, meant they had been kidnapped by a strange alien object, put through a centrifuge and then frozen to sleep before they awakened in the new body, and still moved to save it without a sign of being scared.
- Everything the various normal cells did to try and survive and keep each other alive until the oxygen finally arrived.