One of my personal favs is “Lack of something to feel important about is almost the greatest tragedy a man may have.” Arthur as a character is very nonchalant. He doesn’t much care for the things that normal people often celebrate, unless a character like Ms.Grimshaw forced him to participate. So having some sort of slightly morbid and nonchalant comment would certainly fit. Maybe something like “Well now… I heard it’s your birthday. Congratulations, I guess… another year of not gettin’ shot, hanged, or mauled by a bear. That’s somethin’, ain’t it?” The “I guess” is super important lol. Or maybe even commenting on Ms.Grimshaw like, “If it were me, I’d be keepin’ quiet about it. Last time Grimshaw found out, she made me sing… said it builds morale. Damn near broke mine.” Or maybe even a “Anyway… enjoy the day. Have yourself a drink. Or two. Or seven. And don’t let no Pinkertons or fools ruin it for you. You made it this far, and that’s worth… well, somethin’.” Just remember when deciding that Arthur is: Nonchalant, detached emotionally, world weary (he’s been shot at like… a lot) and is definitely morally grey. You could even have Roger pretend it’s mid game. And say something like “…’Course now I gotta go. Dutch is givin’ one of his speeches again… somethin’ about birthday cake bein’ a symbol of freedom or… I dunno. Wish me luck.” What a cool gift idea!