Always been there. A few more were present too, but I think they got covered up by word bubbles. Oddly enough, they were drawn weeks before I decided to bring back Sporkman full-time. The tiny cameos were really just in-jokes. When I decided to actually draw Sporkman again as a strip, I went back to my FFHH archives to see exactly which panels I'd doodled him in to, so I could use the Amanda dialog from them.
And for the record, there's also a hidden ANDIE in the background here.