I'm on board with the general love for Buchanan based solely on his portrait. Definitely our most whimsical president. Bissell nailed it with the Broadbent comparison. That Old Buchanan portrait also has a Denholm Elliot look, and Buchanan as President would have been like Marcus Brody as President, but the Marcus Brody from Last Crusade, not the Marcus Brody from Raiders.

I'd actually go a little further as far as this portrait of Buchanan goes. He's not just whimsical, he's wacky. This is a man who would have demanded a full-time calliope player be hired and installed in the White House to provide music for him. He would get lost in the Rose Garden at least once a week. He would be very slow to anger, but when he would get angry - and no one would ever be able to guess what might set him off, but it would never be anything about foreign policy or the economy, but something weird like gumballs or those giant swirly taffy things - he would turn red-faced and yell "I AM VERY CROSS RIGHT THIS INSTANT!" and storm out of the room, but would instantly forget that he was mad a few minutes later and would return to delight everyone with poorly-performed magic tricks and playing music with half-filled glasses of water.
President Buchanan Angered By Rabbit (White House Gallery)Buchanan would have been elected after a bunch of people had gotten together and said "Man, wouldn't it be funny if
this guy was president?" and they all agreed to go vote that way. This happens a lot, only this time most of them ended up following through with it. Thankfully, nothing disastrous ended up happening during his presidency, but nothing actually got done either, aside from when he briefly had the columns on the White House painted to look like candy canes, only they ended up looking like barber polls, which greatly upset President Buchanan, who, it turned out, had lingering fears of getting his hair cut. So they had to repaint the columns, but only had red paint on hand and so the White House was very briefly painted red for several weeks in 1859.
Buchanan Leaves Office 1861 (White House Gallery)When it was time for re-election, everybody who had jokingly/drunkenly voted for a "crazy president" last time around agreed that they all still liked Buchanan well enough, but maybe this time it would be a good idea to take this voting thing seriously. As a result, Lincoln was ushered into office and it was silently agreed that nobody would ever bring up that whole Buchanan bit of business ever again.