this episode is often considered one of, it not, the saddest episode of futurama. in it, fry sees a fossil of his old dog, Seymour. So he imagines life in the 20th century with Seymour before he got frozen. So Professor Farnsworth reveals he can clone the dog. Bender becomes increasingly jealous and nearly destroys the fossil. In the end, right before he is about to clone the dog, Farnsworth notices the dog lived to be 15, 12 years after Fry got frozen. Fry thinks Seymour would have forgotten him by then, so he decides to not clone him. We then see a montage of Seymour waiting for Fry, until his eventual death.
I may sound like a jerk, but I never found the end to be all that sad. It is sad, but I didn't really consider it sad enough where it made me feel bad or made me cry. Still a remarkable episode