I finished off the Pinky and the Brain box set a few nights back, and found a third (and very sneaky) Muppet Reference in it.
In the third part of the three part series finalie, they have a concert featuring Swedish supergroup "BAAB" (A clear parody of Abba). Now, they had a cook in another room, who was also from Sweden. it was a short gag, and the animators clearly read "Swedish Chef" in the script and...well... you can see where I'm going with this. They had a dead on likeness of the Swedish Chef as the chef. Same design, same eyebrows covering eyes, same clothes, same color scheme. he didn't talk the same, but clearly was a joke an animator or character designer threw in there.