Edith and Agnes
Margo is the eldest of the three orphan girls that Gru adopts. She was before an orphan horribly treated by Mrs. Hattie. She, like her younger sisters, wished to be adopted by somebody who would love them. At first she doesn't like Gru and his ways and refused to accept as her new father as did he with her as his daughter. She is very disapproving of Edith's mischief, shown where Edith jumps in puddles which gets her and Agnes wet, and also when she breaks a vial of acid in Gru's kitchen. She does join in with Edith's antics if it's against someone she doesn't like. She finds it very endearing when Agnes says innocent childlike things (although she does display mild irritation at Agnes' fixation with unicorns), the polar opposite of Edith who finds it irritating.
Margo and her sisters eventually grew to love Gru and he grew to love them back. Their relationship was broken briefly when Dr Nefario sent them back to Miss Hattie and Margo was hesitant to jump from Vector's ship even though her sisters had safely made it to Gru's ship. After Gru rescued her she grew to think of him as a father and told him she loved him.
Margo is very untrusting of people, taking a long time to warm up to Gru, and also does not trust his minions to begin with. She is quite optimistic despite her difficulty trusting people, telling the girls that they will be happy with Gru eventually. When Gru goes after them when they are kidnapped by Vector, she is happy to see him but is still unsure whether to go back as he gave them away again, but encouraged Edith and Agnes to jump when Gru makes a heartfelt apology. She gives Gru a big hug when Gru finally kisses them goodnight, and says that she loves him, finally viewing him as a dad.
She has a sarcastic sense of humour and wit, shown especially when Gru says not to touch anything, to which she replies 'Uh huh, what about the floor?' and 'And what about the air?', and also when she mocks Gru's accent. She also implies Gru is stupid when he wishes to sell cookies to Vector straight away, whereas they usually go alphabetically. She can be quite judgmental and smart and is very mature for her apparent age. She sees through Gru's lies about his 'dog' and 'cousins', knowing that it isn't a real dog at all, and that his minions clearly aren't human, marking her as quite intelligent. She outsmarts Gru several times by threatening to cause him grief or bargaining with him to get her own way, one occasion where he refuses to read to them and she says they will disturb all night long. She does have a fun loving side, such as throwing toiler paper around Gru's living room, and having pillow fights with her sisters, but her highly protective nature towards her younger sisters means she must act the adult often. Margo is very good at ballet, and enjoys it a lot.