Those were among the revelations in Friday's YouTube interview, which the White House scheduled as a way to reach younger audiences as it promotes Obama's State of the Union address.
Obama appears to be holding out hope that Trump's presidential aspirations flame out.
He said during the interview with Adande Thorne that often, political front-runners are "noisy" or just want attention early on in the process.
"Over time, voters take a careful look," he said. "The closer you get to actually deciding on a president, everybody gets a little more sober."
"It's less entertainment, it's more serious business. This person's going to get the nuclear code," Obama said. "This person's making a bunch of decisions."
He compared the Republican primary to the comment section on websites, where people are constantly "trolling" and where they feel like they can vent.
"We can have big arguments," he said, noting for democracy to work, people need to respect "some basic boundaries where facts are facts" and "we don't make stuff up."
Still catching up on pop culture
Despite his parting excuse at December's end-of-the-year press conference -- "OK, everybody, I got to get to 'Star Wars' " -- Obama admitted Friday he hasn't seen the billion-dollar picture yet.
More galling: when Thorne asked for Obama's favorite Star Wars -- "one through six" -- Obama chose "number one," which he said he saw when he was 14. But according to the series' numbering scheme, Episode One is actually the much-maligned prequel released in 1999.
He did seem familiar enough with the characters. Asked to choose which he'd be, Obama picked Han Solo -- "a little bit of a rebel."
The commander in chief, perhaps reassuringly, also appeared in the dark about the raging online debate over dog pants. But he gamely said that if canines did wear pants, they should cover only the hind legs. Covering everything, he said, would be "a little too conservative."
"Too much fabric," he said, sounding somewhat bewildered.
One area where Obama remains keyed-in: pop music. He chose Kendrick Lamar over Drake, saying Lamar's 2015 album "To Pimp a Butterfly" was the best of the year.
Pads and tampons
It was a question Obama certainly wasn't expecting: Why do some states impose sales taxes on tampons and maxi pads, as opposed to deeming them "non-luxury necessities?"
In her question, YouTube creator Ingrid Nilsen suggested the items were taxed in 40 states as luxury goods, though in reality, those states are imposing regular sales taxes on feminine hygiene products -- a fact many women still decry since the items are necessary.
"I have no idea why states would tax these as luxury items. I suspect it's because men were making the laws when these were passed," Obama said, before transitioning into an explanation of his administration's efforts on women's health.
The issue of taxing tampons and pads, Obama said, "I confess I was not aware of until you brought up to my attention."
Obama is a known science fan, and let his geek flag fly during a talk with YouTube presenter Destin Sandlin.
Asked what his attributes would be if he was an element on the periodic table, Obama described a collection of protons and neutrons in the language of a chemistry teacher.
"I would want it to be stable," Obama said of "Obamium."
"I would want it to be a catalyst, but one that didn't get too hot or too cold," he continued. "And hopefully it would be one that would be useful to humanity, that we could actually use, and wasn't just some shiny object."
What's in Obama's pockets?
Quite a bit, it turns out.
Asked to show off an item of personal significance during an interview with YouTube creator Nilsen on Friday, Obama pulled from his pockets a series of small totems, each of which he said reminded him "of all the different people I've met along the way."
It included rosary beads given to him from Pope Francis, who he met at the White House this fall; a tiny Buddha statue procured upon him by a monk; a silver poker chip that was once the lucky charm of a bald, mustachioed biker in Iowa; a figurine of the Hindu monkey god Hanuman; and a Coptic cross from Ethiopia, where he visited in July.
"I carry these around all the time. I'm not that superstitious, so it's not like I think I necessarily have to have them on me at all times," he said.
But he said they do provide some reminders of the long path of his presidency.
"If I feel tired, or I feel discouraged sometimes, I can kind of reach into my pocket and say yeah, that's something I can overcome, because somebody gave me the privilege to work on these issues that are going to effect them," he said.