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.
Saquon Barkley and Mike Gesicki scored their first career postseason touchdowns during Super Wild Card Weekend.
Several names with established ties to James Franklin and Happy Valley could be in the mix to replace Taylor Stubblefield.