How a show could be called "The Day My Butt Went Psycho" and still be terrible is beyond me.

All right, either I'm a worse anime dork than I thought, or Western animators just can't handle their ass. The Day My Butt Went Psycho is as butt-focused as Bottom Biting Bug, but manages to be intolerable in almost every respect.
In "Ketchup with Uncle Grandpa", I described Cartoon Network's defunct live-action shows as "shrill" - I officially take that back. This is shrill bloody defined. Replace "butts" with "aliens", "robots" or "monsters" (for that matter, butt-shaped aliens, monsters and robots make almost-immediate appearances here) and this could easily be one of any number of Canadian-produced half-hearted, overloud grossout action-comedies. Like too many of its contemporaries, there's also no effort made to conceal that it's bad Flash animation - something which never bodes well.

The Day is based on the beloved children's books that I really don't have the inclination to research. Given the pedigree and general presentation of the show, I'm going to assume they feature similarly-named characters, but with more ambitious storytelling and less reliance on stock slapstick and strained pop-culture references, as seen with Scaredy Squirrel.
The basic premise is that humanity's sorely mistreated buttocks have gained independent sentience and mobility, and now seek to overthrow their former masters - in short, these asses are revolting (I'm willing to bet that joke's already in one of the books, but a gimme's a gimme). Except, that is, for the protagonist's - teenage hero Zack and his benevolent butt Deuce (as distinct from Buhdeuce) are part of an elite society of "butt fighters", with entirely predictable bathroom-accessory-based weaponry and, confusingly, Bottom Biting Bug-like theming. 

Much like Bug, everything from the obvious (chairs and pillows) to the inspired (cymbal nuts) and downright unappetizing (drink lids) - is shaped like a highly stylized butt. In this case, though, society is fighting the same buttocks they honour. Is this an attempt at re-appropriating a symbol, or was this society butt-themed before the uprising? If the latter, perhaps the butts' actual motivations are even less noble than presented...but that's getting pretty far into speculation. If the former, it's sort of like XCOM replacing their emblem with the iconic Grey face, while Ikea redesigns their furniture and dinnerware in simliar fashion and architecture sees a renaissance of the tapering oval. The international strikethrough symbol exists precisely to avoid confusion in circumstances like this.

"Public support seems to be waning since the rebranding, sir."

The Day My Butt Went Psycho is the closest so far to a Western Bottom Biting Bug equivalent...but, of course, here it's humans versus buttocks and everyone yells everything. For all its reliance on standard-issue cartoon plots and characters, Bottom Biting Bug still has actual heart - where The Day feels more like a cash-in than the cartoon made to promote a novelty song and the affiliated products.
The human protagonists bear more than passing resemblance to those of similar Nelvana-Corus property Grossology, and the action segments could have been ripped directly from it (though narrowing the focus from a whole range of hilarious biological processes to butts alone).

Grossology didn't set the bar extremely high, but it was committed to the disgusting factor where The Day pulls its punches. I can also say with absolute certainty that adding Coconut fucking Fred to the situation cannot possibly improve it in any way.

My god...the butt is the coconut! The metaphysical implications are staggering!

Deuce is Fred in nearly every respect, save for the lack of hair and of Rob Paulsen demeaning himself. Deuce yammers constantly, making noises or lapsing into stream-of-consciousness babble as often as he has productive dialogue. He is never still for a moment, arbitrarily destroying whatever object he's near (a cheap source of plot complications, a borderline-malicious Gilligan) and literally bouncing off the walls when idle. Managing to compare unfavourably to the worst example, Deuce represents yet another attempt to recreate Spongebob Squarepants without actually understanding what makes (the less sociopathic pre-movie incarnation of) the character appealing.

I still remembered this line twenty-four years later...what does that say about me?

I can't deny the quality of the puns, at least - the episode "My Milkshake Brings All The Butts To The Yard" (sigh) is built around the unspoken obvious one, as a toilet-water milkshake causes Deuce to become a literal smart ass. "Grandparents Butts Just Don't Understand" stretches further for the title reference and accomplishes even less (making me nostalgic for early Pokemon episodes' inexplicable punning on showtune titles), but successfully teases out an episode-long visual pun on "old farts". That they seemingly strive for a higher quality of ass pun than Breadwinners is the highest praise I'm willing to bestow on The Day My Butt Went Psycho...not out of any particular respect for the achievement, but because there is nothing else that merits praise. Of special non-note are the plots - "smart potion" and "elderly babysitter" are hackneyed enough to be shot down as suggestions at an improv performance, and nothing novel is done with them here. Upcoming episodes include "The Legend of the Buttsquatch", "Beat Box Butt" and "Zackster of Disguise", suggesting this will be a trend throughout the season.

Teletoon is apparently showing The Day My Butt Went Psycho with no concern for order, debuting the series with the first half of episode 3 and the second of episode 7. Said network has never been particularly diligent about continuity, and honestly I don't think it's going to matter that much with this show. Save for potentially explaining the aforementioned butt-theming, any backstory that could possibly be needed is covered in the title theme. As well, this led to an unintentionally (but insightfully) meta joke where the evil leader (the mountainous derriere above) has grown completely cynical of the usual proceedings and is able to call them out step-by-step...in what, to the Teletoon viewer, is the first time he's encountered them. Ouch.