Here's another, though it's not a fish...and not necessarily out of place, just shouldn't have been on my line.
While flyfishing the Firehole River in Yellowstone, my backcast got snagged.
Unbeknownst to me, a few bison had come down to the river behind me, and I had snagged a big bull right between the horns in that "Sideshow Bob" tuft of hair they have there.
I was concentrating so much on the fish rising that I missed them coming.
The bull didn't seem to notice or mind, and a couple of yanks and my 7x tippet popped.
Other odd ones...
Lots of bats, since I like to flyfish at night in E. Wa. every once in a while.
Squalicum Lake in Bellingham put out about twenty little toads in one evening. They were all in the lake spawning, and if they caught sight of your dry fly, they'd paddle right over and grab it. If I saw them coming, I'd pull it out, but I didn't see them all as some were a little slyer than others and swam up to the fly from underneath.
They'd come in with the fly in their lip and both hands holding on to the tippet.
Foul hooked a seal in Whatcom Creek back in my college days. Wasn't able to land him

.
Fishing a beaver pond near Fall City resulted in a six inch rubber worm stuck in the front leg of a beaver. Good fight, but quite short. He broke me off in the trees...
Keep 'em comin'!!
Fish on...
Todd.