Among MLB teams, I'd say the best and most popular mascot is the Phillie Phanatic. Pretty easily too. Shout out to Orbit, the Astros mascot, but the Phanatic has been around for a lifetime and its routines are consistently fresh and hilarious. The Phillies are the gold standard of baseball mascots.
On the other side of the world, the Chiba Lotte Marines in Japan recently unveiled an amazing and also kind of creepy fish mascot at their games. To wit:
It's a giant fish that runs around the field and, for lack of a better term, barfs out its own spine so it can do a dance routine and other fun stuff. For example:
Here are some clips of the fish mascot in action between innings:
I don't know what to think. But I love it. Here are some more images of the mascot:
Alas, the fish mascot is not a permanent fixture at Marines games. The team is reportedly sending the mascot back to the sea for a few weeks.
Sometimes less is more. I'm sure the giant spine-puking fish will be back with a vengeance at some point.