Coffeekitten used to say, “Boys have penises and girls have pajamas.”
He’s 15 now. He’s going to kill me. 
Can he spit? Better yet, can he hork and spit? And has he learned to adjust his package? Probably won’t work if he’s still in diapers, but it’s worth a shot.
Other brother got to him first, he horks, spits then says “I got yur _____ right here” while grabbing his package. 
My husband can move his eyes independently of each other, so he managed to teach that to his older sisters’ girls when they were little. Freaked the hell out of the sisters, as they were squeamish over stuff like that. You’d need to already have that skill to do this, though.
I was once successful in teaching my niece to fill her mouth with food, puff her cheeks then do the Belushi Squirt, (from Animal House and if I have to explain more, then, … well then never mind.) and then say “I’m a pimple, get it?” But only when her other grandma was around - that would be the brother-in-laws mom, she with the pole up her ass.
I wasn’t around to see it, but I heard that when it happened, both my sister and her jerk husband immediately thought of me.
I was so proud.
And you sir - I applaud you for reaching for the sky here.
From MBG - a fellow younger brother.
This Christmas I got to watch as one of my younger brothers (who is in his late forties) tried to teach his 18-month-old grand-nephew (one of my other brother’s grandsons) that the proper way to eat was to put his face down into his plate.
A little later he was demonstrating how to make farting noises with his armpit.
I am a well-practiced uncle but I only have nieces so these may not apply as well:
[ul]
[li]A really loud, obnoxious toy. Drums would be good. The problem is finding one that the little brat won’t tire of quickly.[/li][li]Teach him to hide keys.[/li][li]Get him to say “I have to take a leak” and “I have to take a dump.” When my three-year old niece said “I have to take a weak” it was well worth the daggers from my sister.[/li][li]“Club baby seals!” is a good one if his parents are animal lovers.[/li][/ul]
It is good to see you taking your uncle responsibilities seriously.
You people are terrible, actually encouraging Alienhand to teach the nephew naughty things when he should be teaching the kid how to improve on the useful skills he already has. Why not teach the kid to count backwards?
There’s even a really good song that goes something like “99 bottles of pop on the wall…”
One should never underestimate the value of pop culture. I believe it would be incredibly awesome to hear a young child happily singing “I’m just a sweet transvestite” or telling people they’ve lost the game.
I taught my 3 year old nephew to fake vomit. My sister hasn’t forgiven me 15 years later.
I didn’t see any naughty suggestions, I have no idea where they picked it up from. I blame the TV.
Believe me, after a full day with a three year old, you won’t believe how evil he already is…without your help!
I taught my 3-year-old autistic client (I am a behavior therapist) to take a bucket or empty toy container, breathe heavily into it, and intone, “Luke. I am your father.”
Yes, I do use my powers for evil.
My mother said “the three of you boys (2 older brothers) were all devious children but he is most like you, Alienhand, so what you’re thinking, he’s doing.” From previous experience with the devil spawn, my Mom is dead on.
Smoke cigars.
Teach him to resist putting on his underwear by saying he wants to “go commando”.
There is absolutely no need to teach a 3yo not to put on his underwear. That comes naturally. Number Two Nephew attempted to continue opening Christmas presents with no pants and no underwear, because he’d been forced to stop long enough to get out of his overnight diapers, but didn’t want to waste more time putting on other pants.
SiL was not amused. Well, she was amused, but didn’t let him know it.
Also, the OP had better beware for eventual kids of his own. I happen to be an older brother, and everyone knows that abusing our younger brother is what we do. I’m safe from retaliation; I have no kids myself. But others…
Then just teach the terminology – everytime the kid is pantsless, tell him he should shout out, “I’m going commando!”
I came in here to say this. Fairly harmless and will go away in time.
More importantly is to let him know that real men loudly announce that they like cats. Such as: “I love pussies, and so does my Daddy.” This is simply too good to pass up. Bring another brother in on it.
Rather than just armpit farts, add some pizazz – teach him “Kung-fu farting” (with all due apologies to Carl Douglas).
Nothing like a group of young boys (brothers, you say?) singing, high-kicking, and making fart noises to drive everybody batty.