This isn't really a goof, but does anyone else find it odd that neither Brenda nor her little brother Barclay seem to get their hair color (purple) from either of their parents? Their mom is clearly a blonde, and their dad (I think he's the one on the left) seems to have brown hair. (Perhaps their mom had purple hair earlier in her life and dyed it blonde in her teen years?)
Crandall addresses Hector's mom as "Mrs. Corrio" at the beginning of "Grounded!" In later episodes, though, he refers to her as simply "Hector's mom".
"Grounded!" marks the only-ever appearance of Teamo's dads.