Zeff might not have had a lot of screen time, but he left an impact! What're your headcanons for the man?
Ooohhhh Zeff! I can't not like Zeff. He's big, he's strong, he CAN be scary- but he chooses not too when it matters most.
Zeff was and is still very popular with the ladies—but he has a certain gruff finesse that Sanji doesn't. Mostly, Zeff has the life experience to know when to have a gentle hand and a bit of vulnerability when flirting. He’s a softer flirt. He can say the same outlandish things Sanji does but with the tone and social context to have it land sensually, respectfully, and sincerely. (Sanji will get there with time)
Zeff 💯 gave Sanji the best (worst) sex talk with very creative food metaphors. Zeff was embarrassed, Sanji was confused, and it is only years later when Sanji falls in love for the first time that he suddenly realizes that wasn't a recipe for food but for how to treat a woman right when you really like her. (Maybe one day I'll write it or do a birds and the bees head cannons post for a few characters who definitely got unconventional words of wisdom)
He fiddles with his mustache when nervous.
I think Zeff regrets never settling down and having a family of his own prior to adopting Sanji. I think that when he did adopt Sanji and opened the Baratie it gave him the opportunity to finally feel that dream realized, never really having thought he wanted it that badly or that it was even something he was allowed to want/have/deserve.
Expanding on that---he wants Sanji to settle down and bring him grandkids one day to spoil. He probably has sappy little daydreams about spoiling grandkids and teasing Sanji about parenthood that are exceptionally domestic...but he'll never tell because he's a gruff and tough man after all!
Can you imagine him spoiling a granddaughter and braiding her hair as she braids his beard? Here let me help you imagine:
If Sanji is meant to be a girl dad then Zeff was MADE to be a girl Grandpa.