According to this episode, this is how the following babies acquired their various traits:
Foxxy's Wardrobe: She removed most of it in order to distract Captain Hero.
Clara's Racism: She felt snubbed when all of the other babies decide to go with Foxxy's plan because they felt that as Foxxy was an African-American, she needed a helping hand.
Toot's Appetite: Decided to start eating the first time she killed somebody in order to fill the void in her heart.
Ling Ling's Language: Decided to start talking in a made-up language when nobody listened to what he said in English.
Xandir's Sexuality: Learned he liked guys when he had to kiss Chad's Rebellious Brother Chase in order to keep him fooled.
Spanky's Behavior: Learned he liked to 'relieve' himself anywhere when he had to make it look like the 'Babysitter's' water had broke.
Wooldoor's Appearance: Got it when Captain Hero spun a toy Merry Go Round so much that it removed most of Walter Saget's hair and rearranged his organs so that he needs to go "Whee!" constantly lest he drown in his own bile.
Captain Hero's Quirks: Got it when he wanted to be alone with the body of the dead Babysitter.