Why did WBA redub the A! endtags?

As you see in this embed A! episode (Episode 85, to be exact), new audio was re-used over the old "Ciao-A-Bunga!", 'Flamiel!", "Wanna see me make bubbles with my spit?" (that's the one in the video, audio is "Wanna hear me burp the theme song?"), and "There's a horrible bug on your shoulder!" clips.

But, why did they (Warner Bros. Animation) insert new audio for the old clips after the credits?

Here's de link:

It looks like an attempt at reusing old animation. They probably came up with the new dialogue for the Warners, but wanted to save money by not making new animation for them, so they just recycled an existing clip that would fit with the audio.
This is not the first time it's happened either. The Animaniacs Sing-Along videos also did this for the linking footage: set new dialogue recorded by the voice cast to old stock footage of the characters.

Nice reply, W207. Also, the KidsWB IDs did this, with stock footage of the characters, lip-synching to the dialogue. The Hub promos for A! do this, doing the lip-synching (See the Presidents Day and Labor Day bumpers) as a bonus.

The short answer is: money.

Animation costs money to produce, and while it would have been possible to make all new animation for a 4-10 second outro, Warner Brothers must have figured that they already had the animation of the Warners speaking and that it would be easier and less costly to simply insert new dialogue onto the existing animation.

This has happened on Animaniacs even before the WB episodes. Back in the end of the Fox Kids era, when the lyric in the show's theme song "While Bill Clinton plays the sax" was changed to "We've got wisecracks by the sacks", no new animation was made for the changed lyric. Rather, the animation used was recycled animation of the Warners from the episode "Taming of the Screwy".