Flipper is a tiny black dog who is owned by Elliot Alderson. She is played by a Cairn Terrier called Dusty.
Flipper was originally owned by Lenny "Michael Hansen" Shannon. Elliot saw Hansen mistreating Flipper during his first encounter with him. When he later confronted Hansen with the information he retrieved by hacking him, he also took Flipper from him as part of the blackmail.
Later in the season, while Elliot was performing a "full wipedown", Flipper ate a microSD or SIM card that fell on the floor. Elliot later brought her to a vet, where her microchip number was found. Hansen discovered this while looking for evidence that Elliot was the hacker.
Flipper often stayed with Shayla while Elliot was away.
At the end of Season 1, Elliot answered his door only to find the police, who placed him under arrest for hacking Hansen along with stealing Flipper. Flipper was seized by the police and animal control and likely returned to Hansen.
Flipper was indirectly mentioned several times by Elliot.
Flipper is returned to Elliot by Hansen outside his door, with Hansen mentioning that she was sick/possibly dying and he couldn't pay the vet bills.
In episode 5 of Season 3 (eps3.4_runtime-error.r00), Darlene tells Elliot by phone call that she had to leave Flipper with his landlord due to his mysterious absence over the weekend.
Later, Flipper was shown to have been returned to Elliot as she is seen tottering around Elliot's flat during eps3.8_stage3.torrent