Throughout their days in middle school and high school, Dan and JEN did plenty of playfights. Some recreating their favorite scenes from their cartoons and games. Others they came up with their own stories. Although JEN has been using them to subtly teach Dan how to fight. When he caught on with what she's doing he's actually impressed about the results of the "training". It even led him to develop his own fighting style. When they ran away to Santa Azul they now treat their fights as the real deal. Their rivalry goes back to when they started playing videogames with each other (they still have a rivalry on that department). It now evolves to having friendly street fights and sparring sessions.

JEN: No hard feelings?
Dan: No hard feelings.
JEN: Good.