[3] On 7 July 2023 while attending the Maple Leafs development camp, he suffered a concussion when flattened by another prospect, former Sarnia Sting captain Nolan Dillingham-Morelli.

[6] Hirvonen was invited to the Maple Leafs 2023 training camp, but was assigned to their American Hockey League (AHL) affiliate, the Toronto Marlies, for the start of the 2023–24 season.

[7] In his second AHL game on 15 October 2023, Hirvonen suffered a serious eye injury after being struck by a stick.

[9] At the 2021 World Junior Championship, Hirvonen scored six points in seven games and Finland won the bronze.

[3] In his final tournament, he captained the team at the 2022 World Junior Championship, scoring seven points in seven games and took the silver medal.