In every cutscene you see with Bayonetta sucking on a lollipop, hold down the button corresponding with the color (Green is A, Blue is X, etc) and you'll receive a bonus lollipop item.
Normally, Chapter 8 Verse 3 and Chapter 14 play remixes of BGM from Afterburner and Space Harrier. To hear the original tracks, hold down both LB and LT (X360) or L1 and L2 (PS3) as the proceeding cutscene ends.
Complete the following conditions to unlock the hidden characters below. In order to use them, you must select "New Game" and then the character. All data will be reset for that character only and will not affect your main file.
Unlockable
How to Unlock
Jeanne
Acquire Platinum Medals all Verses in Normal mode or higher.
To unlock the extra costumes, you have to beat all chapters on Normal first. Load your Clear Data, go to "Gates of Hell", and then go to "Rodin's Treasure" menu. You'll see a "Super Mirror" there, which cost 100.000 Halos. Purchase this, and you'll unlock the rest of the costumes (Couture Bullets). To change costumes, press "RB" at the Chapter Start screen, go to "Costume Change", and then choose your costume there.
Unlockable
How to Unlock
d'Arc (Jeanne-like costume)
Purchase "Couture Bullet (d'Arc)" at Gates of Hell for 100.000 Halos.
Nun
Purchase "Couture Bullet (Nun)" at Gates of Hell for 100.000 Halos.
Old
Purchase "Couture Bullet (Old) at Gates of Hell for 100.000 Halos.
P.E. Uniform | Type A, B & C are available
Purchase "Couture Bullet (P.E. Uniform)" at Gates of Hell for 100.000 Halos.
Queen
Purchase "Couture Bullet (Queen)" at Gates of Hell for 100.000 Halos.
Umbra
Purchase "Couture Bullet (Umbra)" at Gates of Hell for 100.000 Halos.
Umbran Komachi (Kimono) | Type A, B & C are available
Purchase "Super Mirror" at Gates of Hell for 100.000 Halos.
Various | Type A (Bikini), B (Bikini) & C (Cheerleader) are available
Purchase "Couture Bullet (Various) at Gates of Hell for 100.000 Halos.
In Chapter 2, after Verse 3 onward on any difficulty, walk around the plaza from Verse 3 outside of combat and stand in front of one of the telephones and input one of the codes below. The left phone by the stairs is used for Weapon unlocks, the right phone for Accessories and the stand alone phone on the other end of the plaza is for Characters. Next to the description is the required amount of Halos you must have in your inventory at the time to unlock the matching secret. All directions are input using the D-Pad. These codes allow the immediate unlock of the listed weapon/accessory/character without completing the requirements.