There's this Achievement that says "play as all the extra toggle characters". Well I've unlocked every character in the game but how do I know who are these Extra Toggle Characters? Also, is it enough to select them, for example, in the Port? I'm not familiar with this whole Extra Toggle thing so I'd appreciate any help. Thanks. (I have the Extra Toggle cheat if this means anything.)
What the extra toggle cheat does is make extra, ancillary characters appear when you cycle through with LB and RB in Free Play level. They won't appear anywhere else.
I haven't got the achievement yet, but it should be good enough to simply enter every level in Free Play, spam LB or RB until you go all the way through back to where you started. Some levels probably have duplicates though, so they might not all be necessary.
Lego Harry Potter: Years 1-4 Collectibles Guide: http://www.gamefaqs.com/xbox360/960495-lego-harry-potter-years-1-4/faqs/60378