In "The Night of the Cadre" Artie accidentally knocks himself out with his own knock-out gas. Jim can't help making a snarky comment, but at the same time he grabs a blanket from the couch and drapes it over his now-sleeping friend.
The toast to Artie at the end of "The Night of Miguelito's Revenge," especially given that it's at least equally a toast to Ross Martin, who was temporarily sidelined due to a near-fatal heart attack.
Jim and Artie's reunion scene in "The Night of the Diva," made even more so because this marks Ross Martin's return to the series after his illness.
Jim's reaction to the reveal that Artie is alive in "The Night of the Murderous Spring" and, especially, "The Night of the Pistoleros."