Sagan

Sagan was 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. Before getting adopted, his name was Kronos.

Sagan was known for being the more well-behaved and smarter cat out of the two, and he often enjoyed sitting on Stephen's lap and laying by the computer wiring near Stephen's work area.

His favorite cat toy was a mouse on a string, which Mal mentions on Day 2819.

According to Day 2914, he slept in the bean bag most nights, which means he probably got more use out of it than Stephen and Mal.

Tragically, Sagan had passed away on February 20th, 2020 due to cancer. He was seven years old. The finale of Fallout 4 was dedicated in his memory.

Trivia

 * 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 did not get scared by fireworks, unlike Kepler, but he does meow a lot (Day 3143).
 * Sagan's birthday was June 4th, 2012. This was mentioned by Stephen on the February 25th, 2020 Breakfast Stream. This was additionally mentioned on the end card for Day 3744.