Sagan is Stephen's cat, named after his favorite astronomer, Carl Sagan. He was introduced in the Vlog on Day 1019, along with Kepler, Mal's cat. His name was Kronos, before getting adopted.
Sagan is known for being the more well-behaved and smarter cat out of the two, and he often enjoys sitting on Stephen's lap and laying by the computer wiring near Stephen's work area.
His favorite cat toy is the mouse on a string, which Mal mentions on Day 2819.
According to Day 2914, he sleeps in the bean bag most nights, which means he's probably gotten more use out of it than Stephen and Mal.
- Stephen mentions on Day 2819 that Sagan is kinda like a bully when he's playing with a toy, so Kepler will refrain from playing with the toy if Sagan is already playing with it.
- Sagan does not get scared by fireworks, unlike Kepler, but he does meow a lot (Day 3143).