Robbie is considered extremely nerdy, shy, and socially awkward, but a good, loyal, and honest friend to others. Robbie has a great deal of trouble with relationships and attracting girls. It is often hinted that Robbie may be in love with Cat, and is proven true in the episode "The Blonde Squad" in which Robbie writes and sings the song "I Think You're Swell" for her. The song is about what a great person she is, and how they get along so well, and that she is all he thinks about. She however, does not appear to get the true feelings behind it, though she does appear to greatly enjoy the song. He is also shown to be the only one who knows Cat's full name, Caterina. He does not seem to have a sense of privacy. His only relative who has ever been seen is his grandmother. It is revealed that Robbie is intolerant to gluten, otherwise known as Celiac Disease. It is revealed in "Wok Star" Robbie is Jewish because he spent his Bar Mitzvah money on leather pants and male make-up. He is also mistaken for a girl in a couple episodes such as "Locked Up", in which he is put on the wrong side of the fence in a jail, splitting the girls' side from the boys' side. In "The Blonde Squad", Cat tells Robbie that he does not "know how guys think".