To do this you go to the extras screen and you then hit extra again and the press L R START SELECT YXYXBABA and when you start a level you will be in 3rd person.
Bonuses
Collect the indicated runes and amount of Lego pieces to unlock the corresponding bonus.
Animal Farm: P, I, R, A, K, A and 30,000 Lego pieces
Big Head: I, R, N, A, K, K and 20,000 Lego pieces
Crazy Colors: V, E, Z, O, K and 10,000 Lego pieces
Disco Craze: T, H, O, K and 15,000 Lego pieces
Human Voice: M, A, K, U, T, A and 60,000 Lego pieces
Invincibility: H, A, K, A, N, N and 200,000 Lego pieces
Makuta Mode: V, O, Y, A, N, U, I and 5,000 Lego pieces
One Hit Deafeat: R, E, I, D, A, K and 150,000 Lego pieces
Piraka Party: I, N, I, K, A and 30,000 Lego pieces
Silhouettes: Z, A, K, T, A, N and 10,000 Lego pieces
Tiny Enemies: RunesM, A, T, A, N, U, I and 20,000 Lego pieces
Unlimited Ammo: A, V, A, K and 100,000 Lego pieces
Defeating Reidak
When facing Reidak the Earth Piraka, you can just stand at the door. Reidak will come to you.