The oldest horse and the youngest horse in one screen.

Great-Grandpa (Sweek)'s grandpa.

Maruzensky → Campaign Girl → Special Week → Cesario → Epiphaneia → Daring Tact

These two have the greatest generational distance between all Umamusume student characters and they are separated by 43 years in RL.
Bolded Cesario since she's now an Umamusume character.
Bolded Epiphaneia since he also became an Umamusume character.

At this point might as well get Campaign Girl too, that would be so cool!