Marco and Holly J. seemed to be on friendly terms, as Marco was comfortable enough to discuss shared interests with Holly J. and call her "HJ" as a nickname. However, she and her boyfriend Declan Coyne used their connection with Marco to get an extension on an essay, which did not sit well with Marco, as his evaluation as a student teacher by Dom Perino was in jeopardy if he did not stand up to his students. After Marco cracked down on Holly J., it can be assumed that they are no longer friends, as he said "It's Mr. Del Rossi to you", and he appeared rather annoyed with her, even though Holly J. did manage to turn in her essay on time.
In Heart Like Mine (1), Marco returned to Degrassi as a student teacher. Holly J. and Declan were seen to somehow know Marco, as they were being very friendly with him. However, they use him to their advantage in order to get special treatment at school. When Marco got in trouble, he told the two he can no longer help them out and Holly J. was upset with him, but they eventually made up. Despite becoming a teacher, Marco was never seen again after this.
In Queen Bees, Marco is seen watching the face off between Holly J. and Paige Michalchuk. He is then seen laughing at one of Holly J.'s insults to Paige. When Paige and Holly J. start yelling "Hun" at each other, both he and Ellie Nash put a stop the face off, by saying "Whoa!" Marco, Ellie and Paige are all shocked to find out that Holly J. is Heather Sinclair's younger sister.
In Party Etiquette, Holly J. is seen at Marco, Ellie and Paige's house party.
- They both watch a show So You Believe You Can Boogie, a parody in the Degrassi universe of the U.S. show So You Think You Can Dance.
- They are both good friends with Spinner Mason.
- Spinner believed that Holly J. had Marco whipped.
- They were both the Degrassi Student Council President in their junior year: Marco from 2004 to 2005 and Holly J. from 2007 to 2008.
- Both were valedictorians at their graduations: Marco in 2006 and Holly J. in 2011.
- Holly J. had a conflict with Marco's former friend Manny Santos.
- They both made their final appearances in #ThrowbackThursday.