New York Mets first baseman Pete Alonso burst onto the major league scene with a record rookie season in 2019. Not only did the “Polar Bear” set the Mets single-season home run record with his 42nd homer on August 27, but he went on to break the MLB rookie record, as well, with his 53rd long ball on September 28. In honor of Alonso’s exceptional performance in his first season as a pro, here’s a look at five other athletes who achieved some of the best rookie seasons in sports history.