I saw this cheat on youtube- and it worked!
You send them 40(LOL!) letters saying
To...
friend friend friend
friend friend friend
friend friend friend
friend friend friend
from...
then wait for 15 mins, go up to them (they should have a white '!' above their head), and they should give you their pic. If it doesn't work wait ANOTHER 15 minutes and try again. Hope this helped, it worked with Pudge! :-D