Octopus

Extraterrestrial lookalikes

The First Doctor frees John from the grasp of an octopus by tickling it. (COMIC: Shark Bait)

Octopuses were a species of cephalopods (TV: Terror of the Autons) native to Earth and other planets. According to the First Doctor, there were no pink octopuses anywhere in all the universes. (PROSE: The Plotters)

On Earth

Professor Zaroff had a pet octopus. (TV: The Underwater Menace)

Julia Fetch admired octopuses and collected glass sculptures of them. (PROSE: The Drosten's Curse)

Elsewhere

On one planet, John was once grabbed by an octopus which restrained him with its tentacles. He was freed by the First Doctor when he tickled it with a feather. (COMIC: Shark Bait)

The Third Doctor compared the Nestenes to cephalopods, specifically octopuses. (TV: Terror of the Autons)

There were methane-breathing octopuses on Neptune in the 32nd century. (PROSE: The Eye of the Tyger)

Keraniums looked similar to octopuses. (AUDIO: "Incubation: Know")