Heartwarming / Highway to Heaven

• Too many to list, but one has to be the one seen in every title sequence afterwards, where Jonathan is walking away alone and Mark rolls up and offers him a ride. Jonathan's delighted beaming really sells the scene.
• When The Boss gives a sign telling Jonathan to let Mark join him. It was clear that neither wanted to go their separate ways but Jonathan felt as though he had no choice.
• Pretty much every time Jonathan is a Friend to All Children.
• In 4x13, Jonathan's truly overjoyed face when Mark wakes up from his coma. Earlier in the episode, he called him "my friend." It's so rare for him to actually say that.