Diego appears less frequently than Robbie, and shares several traits with both Robbie and his older brother Jonesy. He is an inveterate prankster, and in most of his appearances he is seen pulling off a prank of some description, with Jen being a favored target of his. Examples of these occur at the start of "Snow Job" and in "Whoa, Baby." Because he is usually seen pranking with Robbie, and Jonesy appears to pull his pranks alone, it seems likely that he is the planner and instigator of most of the pranks he and Robbie pull off.
Robbie, meanwhile, is a troublemaker of the first order. He is bratty and rude, and frequently makes trouble for those around him. His largest appearance came in "A Crime of Fashion," where he stole a mannequin from Not Quite Naked to humiliate Jude, drove the Clones nuts by pranking people who called the Khaki Barn, and did his best to ruin Jonesy's date with Amélie.
In addition to making trouble and pulling pranks with his brothers, Robbie appears to share another Garcia trait: a taste for women. At the end of "A Crime of Fashion" he is seen spending time with Amélie. In addition to this, he looked up Jen's skirt in "The Wedding Destroyers."
- Robbie has a noticeable gap between his teeth.
- In the episode "Clonesy," Jen makes up a story about Jonesy needing a babysitter for his obnoxious little brother who likes to hit things. While it would be assumed that Jen was talking about Robbie had she not given a name, she instead refers to Jonesy's bratty younger brother as "Marshall."
- Both boys are apparently perverts (which is no surprise, considering Jonesy); Diego was reprimanded by Courtney during the wedding reception for continually staring at her breasts, and Robbie has the aforementioned habit of looking up women's skirts.
- Diego and Robbie have similar tastes in TV; in "Silent Butt Deadly," they are seen watching the same show together.
- Robbie and Diego both have tan skin, Diego has a brown hair color while Robbie's hair is black. From this, it can be deduced that their mother probably had black hair, as Mr. Garcia's hair is brown in color (although he does have tan skin).