Among the main characters, Jigen is the less picky smoker, having a number of favourite brands and a corn pipe. Then why does he get pissed in episode 17 when Lupin (in a hurry due Zenigata appearing from nowhere) buys him Marlboro (one of his favourite brands) Menthol? Because Fujiko smokes exclusively menthol cigarettes, and he was already pissed at Lupin getting him involved with her on the gang's day off.
While one could believe Wataru Uragi had the ability to formulate the Italian Dream's psychosomatic abilities within the pages of a book given enough time, it becomes difficult to believe that Leonardo Da Vinci had the ability, privacy, capital, and time to take the Santa Maria delle Grazie and transform it into a massive gear-based machine that could serve a five-course meal with only voice commands, as well as provide a escape hover boat/airplane hybrid, all based on his centuries old technology. However, consider that 1) da Vinci has a knowledge of the church's original layout because it is the location of The Last Supper, 2) the Santa Maria delle Grazie may still be a public place, but it also has periods of restoration 3) the contraption's design is based off of the Codexes, which he has committed to memory, 4) the invention was most likely financed by his paintings, given he now has the ability to recreate the Mona Lisa without Lisa del Giocondo as a model of reference, and 5) the function of the Codexes were never fully tested at the time they were written because of the lack of technology. As for the time it took to build the contraption, consider the passage of time that occurs in "The End of Lupin III". At least a year passes, which gives da Vinci enough time to formulate his plan and execute it.
Leonardo has surprising little trouble speaking Italian through a few centuries of Language Driftand his first language being Firenze's dialect... Except modern Italian is a direct derivation of Firenze's dialect of the 14th century that was used intact as a literary language until the unification in the 19th century. To him, who had to be fluent in 14th century Fiorentino due work necessity, the language drift is less than a century and half, and Leonardo's genius could easily cope with it.
In episode 10, Belladonna reveals that she was taken in and raised to be a Child Soldier under Fago, the instigator of the episode's events. This wouldn't be anything too abnormal, up until he attempts to molest her and then has her beaten up when she resists, ontop of the revelation of the bomb planted to her heart he only makes just then. But they use very specific words here when he asks if he should "cheer her up again," all but stating that the man's basically committed repeated rape on an underaged girl that he also personally conditioned and put a gun in the hands of to kill other people for him; a younger Belladonna even has a brief moment when Goemon does his first pinky swear with her that implies she Hates Being Touched. Jesus.
Episode 24 is already freaky enough given Da Vinci's takveover of the Italian peninsula by putting everyone asleep...which brings us to this question: did any of the asleep people got hurt or even KILLED while asleep if anyone in the Italian peninsula were partaking on an activity that could risk death?