Here are what I consider to be the Top 5 Otters in US history. List in reverse order of significance:
5. Obadiah Otter - he was a curious otter who happened upon the Donner Party in 1846. These were the first humans Obadiah ever encountered and as it worked out also the last. He is historically significant because he kept the Donner Party from resorting to cannibalism (for an additional 36 hours).
4. Jeremiah Otter - his wife and adopted son were killed by a Crow Indian raiding party. He spent the rest of his life tracking down Crow Indians and ripping out their necks while they slept. He became a Rockie Mountain legend and some say a myth. Some even say he's up in those mountains still.
3. Sergeant York Otter - while it was widely reported that the Navy experimented with strapping bombs to dolphins it is lesser known that the Army had a similar project utilizing otters. Sergeant York Otter was named after the WWI hero and died during a training accident.
2. Sacagawea Otter - the only female otter on the list. She was the mascot of the Lewis and Clark expedition party until she was killed by Meriwether Lewis and her pelt was exchanged for some corn meal.
1. Bedford Otter - this otter is significant because as a youth he used to live in a pond in Bedford Falls and one winter when he was young he was poking around under the ice to the point where he caused a few cracks. These cracks broke when a young Harry Bailey was sledding onto the ice. In one timeline Harry's older brother George was able to save Harry but in another timeline George wasn't around to save Harry. In a third less publicized timeline - Bedford Otter didn't nose around under the ice and Harry never fell into the icy waters. In that timeline George Bailey was a whole lot less necessary to the happiness of Bedford Falls.
Just missing the list - Otter from Animal House.