*Please add more photos*
Robbie is commonly depicted in an outfit similar to that of Gravity Falls Wendy except he has glasses. He wears a green flannel, a white shirt, tight jeans and dirty boots. Some fan-art shows Robbie in a gray and white suit with his glasses. In both, his hair is shorter and does not cover his eye.
Robbie's personality differs with the way he was drawn. While in his Wendy-like outfit, he seems more laid back, and a lot more shy. But, when's he's dressed smart in his suit and glasses, Robbie is stiff, smart, and judgy. He seems to work for Gideon Pines because in one drawing he's checking out Journal 3.
In the picture to the right, Robbie is talking to Reverse Wendy, and we can see the outfits exchange and the shy personality of Robbie.