As a game paying homage to old games Scott Pilgrim of course includes the seemingly forgotten concept of cheat codes. Here are all the cheats I know of.
 
Unlock Joseph's Bedroom/The Studio (the house with a radio tower):
Enter at map screen.
L1, L1, R1, R1, L1, L1, L1, R1, R1, R1, L1, R1
 
Unlock Survival Mode:
Enter at title screen.
Down, Up, Right, Down, Up, Right, Down, Up, Right, Right, Right
 
Unlock Boss Rush: 
Enter at title screen. 
Right, Right, Circle, R1, Right, Right, Circle, R1
 
Have The Power of Love sword at the start of levels:
Enter at title screen. 
Square, Square, Square, X, Circle, X, Triangle    
 
 Turn coins into animals:
Enter at  title screen.
Up, Up, Down, Down, Up, Up, Up, Up   
 

Following cheats are cheats I haven't tried (so I can't confirm that they work).

Enable Blood Mode:
Enter at title screen.
X, Circle, X, Square, X, Circle, Circle 
 
Players can select the same character:
Enter at title screen.   
Down, R1, Up, L1, Triangle, Circle

Ooh cool! I'll try those later :)

I imagine the use of the Konami code would be right up this game's alley, what with the density of classic video game references and all.  You'd have to swap the A and B out though, probably for the X and O.

Maybe the Konami code unlocks the Boss Rush mode lol!  It seems like no one has unlocked Boss Rush mode for the game yet...not sure though...

i Heard that if you have ssf4 in the disk tray while you play and you switch to hd remix while playing and switch back fast enough you can play as ryu!

What does Josephsroom/studio have? I'd guess it's a place to listen to the music/sounds?
 
 
I was going to make a thread for this but it kind of goes in well enough though not a cheat (probably).
 
Has anyone figured out how to unlock the 6th character yet? I get you get <redacted> if you beat the game with Scott,Kim,Ramona, and Steve Stills, but there's a 6th character according to the "Character data" section of options.

" What does Josephsroom/studio have? I'd guess it's a place to listen to the music/sounds?  I was going to make a thread for this but it kind of goes in well enough though not a cheat (probably).  Has anyone figured out how to unlock the 6th character yet? I get you get <redacted> if you beat the game with Scott,Kim,Ramona, and Steve Stills, but there's a 6th character according to the "Character data" section of options. "

Nah beating Mr. Chau on the map just unlocks him as a Striker (Like Knives, assist moves)

" What does Josephsroom/studio have? I'd guess it's a place to listen to the music/sounds?  I was going to make a thread for this but it kind of goes in well enough though not a cheat (probably).  Has anyone figured out how to unlock the 6th character yet? I get you get <redacted> if you beat the game with Scott,Kim,Ramona, and Steve Stills, but there's a 6th character according to the "Character data" section of options. "

I was trying to convince myself not to buy this until I had a steady cash flow, but y'all finally fucked that up for me. Thanks. Now I have to go play a video game. >:(

josephs bedroom is awesome with all the music and that
but the power of love cheat doesn't work for me :/

" josephs bedroom is awesome with all the music and that but the power of love cheat doesn't work for me :/ "

The code to unlock the music testing mode may actually be only 
L1, L1, L1, R1, R1, R1, L1, R1
 
Because if that's true it is a referens to the DDR cheat code 
Left, Left, Left, Right, Right, Right, Left, Right

" @gike987: yeah i've tried it lots of times and it just doesn't workalso the josephs bedroom cheat does have the L1 L1 R1 R1 at the start also did any one notice that when you have blood mode turned on the blood that spurts out is in the shape of a heart "

" @Ulong said:

" What does Josephsroom/studio have? I'd guess it's a place to listen to the music/sounds?  I was going to make a thread for this but it kind of goes in well enough though not a cheat (probably).  Has anyone figured out how to unlock the 6th character yet? I get you get <redacted> if you beat the game with Scott,Kim,Ramona, and Steve Stills, but there's a 6th character according to the "Character data" section of options. "

Mr Chau, Im pretty sure is unlocked by beating him, and Nega-Scott is unlocked by beating the game with the 4 characters you start with. "

" @lilbigsupermario: you have to beat it with each different character as player one "

Enable Blood Mode:
Enter at title screen.
X, Circle, X, Square, X, Circle, Circle 
 
Players can select the same character:Enter at title screen.    Down, R1, Up, L1, Triangle, Circle "

Boss Rush mode cheat has been revealed! 
 
According to gamefaqs.com: 
 

dont know if this has been posted but cheats DO NOT disable achievements. just used the sword cheat and got the ach where you defeat patel without losing a life.  
 
kinda feel guilty...but this game is kinda hard!

" dont know if this has been posted but cheats DO NOT disable achievements. just used the sword cheat and got the ach where you defeat patel without losing a life.   kinda feel guilty...but this game is kinda hard! "

Can I still unlock achievements if I use the love sword?

" Can I still unlock achievements if I use the love sword? "

" @Shadow: There is an achievement (forget the name) for completing an entire level without getting hit once.  I imagine the sword would come in handy for that. "

" Boss Rush mode cheat has been revealed! 
 
According to gamefaqs.com: 
 

Boss Rush

Right, Right, Circle, R1, Right, Right, Circle, R1

 Most likely in the title screen.  Although I haven't tried it yet :D "

It's like everything got awesome when I returned to the US. Thanks for the codes. :D Maybe a print magazine will reveal that final tidbit.

Do these disable the achievements? I would assume so.