One of the Lincoln Vlogs reveals that he was adopted because Lana found him and cried until they got to keep him, and that he was named after Cliff Sterrett in-universe as well as out-of-universe.
In "Head Poet's Anxiety", Cliff is present six years ago (when Luan is eight) and appears to be a kitten. This reveals that he is about six years old (since cats are considered kittens until they turn one) and that Lana found him when she was a baby.
"Home of the Fave" reveals that Cliff sometimes poops in Lynn Sr.'s shoes.
