Animated characters who disappear with no explanation

[Princess Buffy]

IIRC in the second season of Ducktales, Doofus was only in like one or two episodes. Upon rewatching some old episodes I had on tape, that is kind of a good thing and I really don't care what happened to him.

[Jamal Timbukkake]

A good chunk of DW's Rogue's gallery disappeared with the 2nd ABC season. Bushroot, Tuskernini, Liquidator, Quackerjack, etc.

[FlurryOfDancingSnow]

I could be wrong but didn't she also appear in the pilot of Batman Beyond?

[Gott@ put m3 0n (yerpie)]

I'm not sure if this counts, since the characters weren't completely removed from the show, but nonetheless...

After the 1st season of Heathcliff and the Catillac Cats, Hector, Wordsworth and Mungo stopped appearing in the Heathcliff shorts, and were from then on relegated to only appearing in the Cats & Co. segments. Their roles in the Heathcliff shorts were taken over by a trio of previously unnamed alley cats who were later dubbed Lefty, Knuckles and Raoul. No explanation was given for the change, it just happened.

Also, Johnny Test's first crush, Janet Nelson, Jr., pulled a Houdini after the show's first season. Janet's only post-season 1 appearance was a non-speaking part as an extra in "Johnny Zombie Tea Party".

[3n1gma]

No, I'm pretty certain the reason they dropped the Campbells so quickly was because Jeff genuinely liked Meg, and we all know she can't possibly experience happiness in her life. Ooh, God forbid she be anything other than the writers' personal punching bag! Just 'cause they don't want to put in the effort to give her any decent stories!

I said it before, I'll say it again - it shouldn't have been Cleveland who got the spin-off.

[writerinthealley]

Yeah, that would've been a good idea... take a character that the writers have proven they can't be bothered to write for, and focus an entire show on her.

Maybe if they hired some of the writers from Daria...

[D595]

Remy Buxaplenty from The Fairly Oddparents. After "Operation: FUN", he disappeared without a trace, even though his godfather Juandissimo keeps appearing.

Also, the police force in The Batman seemed limited to Gordon after Season 2. Yin and Rojas never appeared, and Bennet disappeared after reforming.

[Purple Rayne]

"Meg, who let you back in the house?"

I'm sorry, but no one - aside from the few internet fans who perhaps harbor a crush on Meg and think she deserves better - would watch a Meg spin-off. Sometimes they do go a little too far with the Meg bashing on the show, but at the very heart of it Meg has been an aggravating, whiny pain in the butt from the very beginning. A spin off featuring her would not work.