He is Terence with a dark blue mask with yellow stripes and a yellow W. In Angry Birds Space, he is the same as Angry Birds Friends but it's Incredible Terence without pupils, hence why he is green in that game.
He appears in Angry Birds Friends! as a Power-Up, as said above. He has the same strength as Terence but has an enhanced speed and shockwave. After he does something, he will say 'POW, SCRATCH', OOF', AARGH and other comic exclamations. He can brought by the following prices:
Wingman is one of many power-ups to be an extra bird. Others include Shockwave, Telebird, Call the Flock and Clone Bird.
Wingman originally had many different mask concept designs for Rovio to pick as the design for Wingman. The fourth one in the second concept art picture above ended up being used.
In Angry Birds Friends, Wingman is very overpowered when both the Power Potion and King Sling is used on him.
Use Wingman, and after he appears use both the Power Potion and King Sling in any order, and you will have created the most overpowered bird in the game. He can mow through and obliterate glass, wood, stone, pigs and other objects without losing speed, and will only stop when he collides with the wall, ground or ceiling. This combo is very useful for getting three stars in a tournament level or beating someone in Star Cup due to insane amounts of points, and is considered by a few to be the most broken, overpowered power-up combination in the entire game.
Sling Scope is optional, but it is mostly used to aim Wingman where the biggest structure is so he can destroy it and rack up massive amounts of points.
His normal counterpart, Terence, can be used as a sort of substitute for Wingman if you can't afford him.