This wasn't the first time he had done this. Diguising himself as his carefree and friendly twin brother was what he did when he wanted to find out more information about the earthlings. To get to know them better. All he had to do was to take Maru's headband and make his hair more messy, and there it was. He was identitical to his brother. He was doing it for the future of Simurians after all.
This was however, personal. It was about you. He wanted to get to know you better, without sacrificing his cynical, aloof demeanor. He didn't want to give you idea that he was interested (he was). So, he has been doing once in a while, pretending to be Maru and letting himself indulge a little. Yes, it wasn't the best idea from him, but he couldn't help himself.
"So, what do you think of Cross?" He asked you while walking next to you, assimilating the best Maru nonchalant tone and bubbly expression as he could.