Each Larry the Titan you find in a level, unlocks concept art in the gallery extras menu.

to do good moves with each titan hold down triangle. For a quick big attack hold down O. For big fighting attack hold down square.

All you have to do is just play through Story Mode and eventually unlock characters.

Multiplayer Mode Characters - Play through Story Mode

when playing against plasmus always pick up crates and throw it at him. thats a good way to beat or weakin him.

To defeat Ternion, you must stand on 1 of the 2 platforms that are near the end of the 4 sections and that will take down his shield. Then, you pick up an explosive crate while his shield is down and throw it, keep doing that until he comes out of is shield.

City Cathedral - Complete the City Night Showdown level
Larry's World - Complete the Danger Yard Level
Mad Mansion - Complete the first part of Jail of Horror Level
Mumbo's Big Top - Complete the second part of Magic Mayhem Level
Raven's Mirror - Complete the Thriller Driller Level
Titan Tower - Complete the Slade Ambush Level
Slade's Lair - Complete the Final Clash Level
Sky Needle - Complete the Titan Tower Level
The Hive - Complete the Hive Academy Level