You have any idea how many Transformers that could be? I’ll go with Jhiaxus, though.
"What’s this?! Everywhere you go, scores are resorting to mental institutions.
Inattentive salesmen lose potential clients.
Frustrated comedians ruin jokes.
Muttering fools nurse old grudges…"
Batman, referring to Prometheus after slipping him the wrong skilldisk. JLA, don’t remember the issue number.
“How does it feel to have someone throw up on your soul, Henry?”
Koffing, you are correct!
That would be hellboy box of evil
my turn
“I’m a nasy piece of work chief. Ask Anybody”
Lear’s Fool: John Constantine, Swamp Thing #37, Moore/Totleblen
Koffing: Is that Cassandra Nova talking to the Beast?
Ukelele Ike’s choices are killing me. Hey, if they’re from Morrison’s THE FILTH, I tried issue #1 and it didn’t take.
Oh, sure, but it’s a classic Furmanism, yes?
Nah, the best Jhiaxus quote has to be his end-of-the-world tirade from TF:G2 #12. “YOU–!” 
I’d offer another quote, but without my comics here at work, I can’t recall anything with enough accuracy for the job… 
That sounds like Dr. Doom’s answer to the Enchantress’s question in “The Secret Wars” issue # 7??
Am I right?
Well, if so, I’ll throw another one out there -
“Woman, have you not foreseen that you are to marry this tree?”
Krokodil’s quote must be from Rebis in the Morrison-era Doom Patrol (does that really qualify as a mainstream DC book?), though I don’t know which other DP member is responding. Crazy Jane, perhaps?
My turn:
“After all, who doesn’t like roses?”
“Yumpin’ Yiminy”
Ultra Arcane Obscenely Difficult Ultra Obscure Comic Book Quote
Regularly said by one of the characters.
Mwuhahahaha!
Katzemjammer Kids?
I think Fibber McGee’s quote is from Transmetropolitan, spoken by Magical Truthsaying Bastard Spidey, in … issue 31?
Sheeeeesh. Nobody reads underground comix anymore?
Way to make me feel old.
I do, Ike (they’re my dad’s 
)
I don’t know your quotes, though.
I will however throw this one into the mix (double points if you get this):
“Me too, I ate one sour too.”
More clues forthcoming if requested.
Close to the right time frame but off by a country mile. Clue: Think comic book, not comic strip.
PS: Wasn’t it the Katzenjammer Kids?
Ahhhh, that one’s easy.
Fat Freddy, the chubbiest of the Fabulous Furry Freak Bros., after trying desperately to remember a new telephone number for Dealer McDope.
Freewheelin’ Franklin had just responded to Phineas’s query about who had eaten all the pickles he’d bought.
Dint even have to look that one up.
Full points… and I thought that was tough!
Nice to meet a fellow freak fan on the boards… I thought I was the only one!
OK, here are some tougher ones (I may be paraphrasing these slightly):
“Rub off the black crap to see if you’ve won.”
“I’m still just plain old mom to the kids.”
“I hate to break up this heartwarming scene, but there’s an army of cops coming.”
Again, clues will be forthcoming if requested.
Also, if you have any obscure freak-o-rama stuff to test me with then go ahead.
Forgot to add: The above are not necessarily freak brother quotes.
Let’s see…I know the middle one, it’s Missus Yahootie after she was struck in the head by Meatball. From an early issue of ZAP Comix, either No. 0 or No. 1, back when it was entirely Crumb’s work.
The other two are darn familiar, though…give me time to reflect.