Ronnie is a boy Quinn Morgendorffer attempts to con into taking over her babysitting job in the episode "Pinch Sitter". He's hesitant at first, and after Quinn attempts to compliment him by saying how "nice" and "sincere" he is, he remarks, "You're never gonna go out with me, are you?" Quinn confirms this before Daria mentions that Skylar Feldman was asking for her. Ronnie then realizes that Quinn was trying to get out of her babysitting to date Skylar, and angrily suggests that she ask her sister, since "She seems like the type who has plenty of Saturday nights free."
Ronnie goes on to appear in background of numerous scenes. He was one of the few people watching Bing and the Spatula Man (during their attempt to get Upchuck a date on the radio) who seemed unimpressed with the show ("Jake of Hearts"). He is similarly unimpressed when Kevin cocks up in "The F Word".
Ronnie in Fanfic
Ronnie doesn't often appear in fanfics, except as a cameo relating to his role in "Pinch Sitter". He gota supporting role in Shiva's Sexy Daria (as a love interest for Scarlett) and a starring role in Shiva's Unexpected Hookup. In a Random Pairing Iron Chef challenge, Princess Pasta paired Ronnie with Tori Jericho in To Each Their Own (and also established them as old friends).