Hank

Hank is the deuteragonist of Finding Dory. He is a stern but good-hearted octopus.

Finding Dory
Hank meets Dory in the quarantine tank, where he tells her of his plan to take her place in Cleveland and spend the rest of his days in a quiet tank. He carries Dory around in a coffee pot, sippy cup, and clear Solo cup as they travel around the Marine Life Institute and ends up in a kiddie touch pool where he inks himself. He ends up separated from her and gets captured, but manages to escape with Dory's help. The two then hijack the truck and drive it into the ocean, freeing all the fish. He is later seen taking Mr. Ray's place as a substitute teacher.

Official Bio
"Hank is an octopus. Actually, he’s a ‘septopus:’ he lost a tentacle — along with his sense of humor — somewhere along the way. But Hank is just as competent as his eight-armed peers. An accomplished escape artist with camouflaging capabilities to boot, Hank is the first to greet Dory when she finds herself in the Marine Life Institute. But make no mistake: he’s not looking for a friend. Hank is after one thing — a ticket on a transport truck to a cozy Cleveland facility where he’ll be able to enjoy a peaceful life of solitude."

Trivia

 * When camouflaging, Hank changes not only his color but his shape as well. This is similar to the real-life mimic octopus, which uses this technique to hide from predators and imitate more dangerous animals.
 * The reason Hank only has seven tentacles is because his body and tentacle models were developed separately. When they tried to attach eight of them to his body, they found that only seven fit, so they simply left him with seven and just worked the missing limb into his backstory.
 * Hank did not know that he, in fact, has three hearts (which is brought up by Dory) until he sees a sign near the Open Ocean exhibit that says so, which helped Dory remember where the exhibit was.