Parody occurs when someone (most often legally) copies the style and/or elements of someone else’s creative work to make fun of it.
People often assume that parody is critical mode, but as the “Harry Pothead” example suggests it is often very mild-mannered and need not be critical of the original in any way.
Using parody is a double-edged sword if you actually want to criticize something. The author Vladimir Nabokov once said “Satire is a lesson; parody is a game.” Like a game, parody often is more a matter of fun than criticism, and parodies can serve to reinforce the values of what they are parodying by reproducing and relegitimizing them. For instance, when Weird Al Yankovic parodies a popular song, it essentially adds to the song’s visibility and pervasiveness in culture and could even draw new listeners to a song they otherwise might not have listened to.
Be careful you don’t make another “ad” for something you want to attack.