Overall, I think things have still been going strong with the past few episodes. 

I initially didn't notice the earmuff/aardvark ear thing at first, but I've been chuckling about it ever since it was pointed out here.      Whether or not it was intentionally subtle humor or just plain oversight, I've not a clue.

On that note, favorite moment: Brain pointing out to Muffy that there are no monkeys in North America, followed by Muffy recounting an "amazing" story about how her father was bitten by a monkey.  Let's never mind the fact that Muffy and her father are both monkeys...

I actually think having Chip around detracts from Muffy's character.  She functions better as a single child, as it amplifies her "all about me" aura.  Seeing her fawn over an older brother just seems out of character for her.  Although, I'd imagine taming her character in that manner might make her more likeable to a lot of viewers.  Nonetheless, I've grown to rather appreciate her horrible little self over the years.

I also really appreciated the Gallagher homage.