Whether it's playing pranks or encouraging your child's wildest Lego plans ("Sure, we can probably build a castle that reaches the ceiling! I'll get the ladder!"), grandpas are really good at scheming with children and encouraging children to scheme. It's cute, even if moms and dads don't always appreciate it. But who better to learn from than grandpa, right? He'll ensure that shenanigans stay shenanigans and don't progress into tomfoolery.

It's funny when they mess up the lingo, to be sure. For example, my Poppy somehow got it in his head that "Siri" is "Nelly" and regularly asks us to "Ask Nelly." Adorable, right? But when a grandpa really commits and can name all the Pokémon, or knows who all of Barbie's friends are, that's absolutely adorable and really, really cool.

My entire life, my granddaddy has done this trick where it looks like he's removing and then reattaching his own thumb. The dude really sells it. It's classic Granddaddy, sure, but it's also a classic grandpa move, right up there with stealing noses and taking pennies out of ears and shamelessly entertaining kids with card tricks. Just performing these magical illusions is pretty cool, yes, but eventually teaching a kid how to do them is something that separates cool grandpas from very cool ones.

The day my granddaddy showed my son how to "remove his thumb" you'd think he'd been let into a secret society of magicians.

It's not just parlor tricks. All grandpas have some distinguished, old dude knowledge. My dad, for example, is really into sports and has loved teaching my kids how to pitch a ball or catch a pass. My father-in-law is an entomologist, so any time we see a neat new bug my kids urge me to take a picture so we can "ask Papa." I'm sure all grandpas have their specialty set, from cars to trains to history to crafts. The cool ones will find their own interests to be a great bonding opportunity.

Any man can read a bedtime story, but it takes a Cool Grandpa (like my dad) to read a bedtime story complete with intense, individualized voices for every single character and tons of emotion breathed into every line.

Sleepovers at a cool grandpa's house are the stuff of legend. There are movies. There are blanket forts. There are board games. Those aforementioned awesome stories? Naturally. Is there junk food? There is only junk food. You shan't find a vegetable within a 500 yard radius of the property line.

In general, men don't like appearing foolish. They can be quite self-conscious, bless their hearts. Cool grandpas? Cool grandpas DGAF. "What's that, sweetie? You want to practice ballet. Sure! Do have a tutu that will fit me?"

"Tea party? Of course!"

"Pretend to be your Pikachu! Well, OK. I mean... Pika! Pika!"

The coolest grandpas respect the boundaries laid down by parents. As a mom, I couldn't tell you a grandpa was cool if he had flagrant disregard for the rules, but I will admit that the coolest grandpas are going to test every possible loophole and boundary they possibly can.

"Explain to me how a potato chip isn't a vegetable. You can't because it is. I rest my case."

Honestly, it's their right and I get it.

Growing up, my Grandpa would never come to our house without some sort of sweet. Charms lollipops, Dove chocolates, Entenmann's doughnuts. This dude was not the warm cuddly type — he was 5'2" of pure, WWII-vet fury — but he was still a cool grandpa because he loved us and even if he couldn't always say it, he could make sure we knew how he felt with treats.

The coolest aspect of a cool grandpa is this dichotomy: an old crank who nevertheless can set that on the back burner for the grandchildren. Without the crank-factor, the coolness just doesn't stand out as much.