To "do a Mientkiewicz" in baseball is to make off with the game ball from a big victory, usually unjustifiably. It references the time when Doug Mientkiewicz, a back-up infielder on the 2004 Boston Red Sox, kept the game ball from the team's World Series victory. The franchise threatened to take him to court for the ball before Mientkiewicz finally gave it to the Hall of Fame.
The back-up catcher did a Mientkiewicz and hid the game ball in his equipment when no one was looking.
The insuppressible emotion experienced upon sight of an unbelievably cute animal that causes the brain to overload and create a sensation of rage at the world for having created a creature so incomprehensively adorable and not placed it directly in your lap. Can only be relieved by punching or smashing a nearby object and then talking in a crazy voice about how you want to smash said animal's face or pull its ears off when in reality it is so precious that if it crawled up to you you'd just dissolve into a puddle of goo.
Person 1: "Look at the fluffy baby bunny on Zooborns!"
Person 2: ***CUTE RAGE*** "OH MY GOD IT'S SO PRECIOUS I WANT TO RIP ITS LITTLE EARS OFF!"