This picture is enough to make me laugh (I'm still laughing writing this and whenever I see it again!). Mr Gullible is the story of a simple single man from a small town in Iran travelling to Tehran to find a suitable girl for marriage. He is always wearing a clean suit and fedora hat and tie and speaks with an accent and is overpolite. He also constantly says "wonderful wonderful" (in Persian: ajab! ajab!) in a memorable funny way. He has a small notebook full of poems he had wrote with his nice handwriting and shows it to anyone. He's a simple office clerk and tells everyone his boss promoted him because of his handwriting.
Well Mr Gullible in my opinion is not very gullible. He might have made mistake in choosing the right girl but he was so respectable to her. He didn't make advances to the girl even if she tried to. When he found out who she really is he didn't shout at her or beat her. He respectfully asks the girl if she quits what she does he'd marry her and take her to her hometown. He is not violent to her. Also in the scene his friend wants to cheat him he refuses to sign the contract. So smart! He's not a fool then.
Overall I think Mr Gullible is not gullible at all. It's just the world around him being too bad.