"Le Tourment" ("Torment"), where Arthur manages to convince Perceval that yes, he does like him, even if Perceval regularly annoys the hell out of him. Then the long, awkward (to Arthur, anyway, very much so) Man Hug takes it back to Funny mode.
Perceval: Ah, well, you see, my folks' neighbours have four sons; there's one who's a bit retarded, and he's their favourite. Arthur: Yeah, I can understand that.
A different episode has Perceval ask Arthur for help with a letter to his father and his uncles: his grandma is dying and wants to tell her children that she's always loved them, even if she never found the words to say so. And of course, it ends on a funny note when having exhausted all possible metaphors, Arthur asks what the relatives are like. "Well, they're kind of dumbasses."
Perceval's monologue in "L'Habitué" ("The Usual Customer"). "I'm no good at tactics or archery, but I damn well know what it's like to love someone."
"Pupi": Arthur in disguise sees a puppet show with Caradoc and his family. At the end of the episode, he watches it again... without the disguise, accompanying the children.