Allar (+1700) has higher Heisman odds than Michigan quarterback J.J. McCarthy, who lands at +2200.
Brown will be remembered as a defensive cornerstone that helped take Penn State's defensive to the next level.
Singleton and Carter earned the honor after their star-studded true freshman seasons.
The former high school standout appeared and started in just one game during the 2022 football season.
The addition of McClain gives the Nittany Lions their second transfer pass catcher of the offseason.
The 6'2", 220-pound linebacker chose Penn State over Big Ten programs Michigan and Ohio State, as well as Pitt and Boston College, among others.