5. Grandpa's Pipe (Back To School, S4, E1)
Another one relatively popular online, but when a cartoon makes a hidden drug reference, you can't ignore it, and this reference isn't the most obscure. Granted they don't have Grandpa Phil blazing one up on screen, but his reference to being at Woodstock having killed off the last of his brain cells is as blatant a drug reference as you're likely to find in a Nickelodeon show from the 90's. I guess it also helps to explain why Grandpa Phil's such a bizarre old fella as well. It does beg the question of whether he still tokes on Mary from time to time, though, even at the grand old age of 104 (I'm joking, I don't know how old he is). Maybe he was nicknamed Steely Phil for his steely expressionless look? Or maybe it was his fondness for pipework... http://www.youtube.com/watch?v=NVRoBes9vJ4