Dad gummit, that's funny!
Enter MAD Magazine.
The first rule of a parody ad – according to the MAD editors – is that the original ad has to be well known. Readers have to know what you're spoofing.
The second rule for a successful parody ad is that it must trick viewers at first glance into thinking they're looking at a real ad.
In the '50s, around the same time MAD transitioned to a magazine format, Crest Toothpaste with Floristan launched it's "Look Mom, no cavities!" campaign. Not long after, MAD readers saw a nearly identical ad with the headline, "Look Mom, no more cavities!"
But a closer examination revealed that the toothpaste was called Crust Gumpaste with Fluidsteel, the Norman Rockwell illustration of the smiling teenager was actually by Norman Rocknroll, and the smiling boy had no teeth. The copy said, "Crust Gumpaste takes the place of teeth by coating them with a hard white enamel finish!"
Even the fine print was parodied. The usual "Guaranteed by Good Housekeeping" seal was replaced with, "Guaranteed by Good Housewrecking."
Spoofing even the tiniest elements was the key to making a parody ad work.
I sense thread drift, so it seems we need a critter to stay on topic.