Fred Flintstone and Barney Rubble have accrued quite a lot of commercial credits over the decades:
Cocoa and Fruity Pebbles
Flintstones Chewable Vitamins
And now while I was in Connecticut, I saw them singing the praises of Midas Mufflers.
Maybe Inner Toober Hugh D. is right: there should be another 'Sliders' universe in which to stow away all the TV characters who practice serlinguism; who step outside of their surroundings to pitch products to the viewers at home.
Fred and Barney would certainly qualify to have doppelgangers in that brave new TV world which Hugh has dubbed "the ad-verse". None of the products they hawked would have been found back in the Stone Age. They would have had the prehistoric equivalent, like Winstone Cigarettes or Midasrock Mufflers.
(That type of adjustment for products happened in the opposite direction of the Tooniverse timeline. In the year 3000, Philip Fry will enjoy breakfast with Admiral Crunch and Arch-Duke Chocula.)
Someday both Fred Flintstone and Barney Rubble will join Pebbles Flintstone Rubble in the TV Crossover Hall of Fame. But it could be argued that they could enter twice - as their versions in the Tooniverse and as their pitchmen in the "Ad-verse".
And not that it seems likely right now, but even their live-action versions in TV movies might one day meet the rules for qualifying. Maybe the Mark Addy/Steve Baldwin version of Fred & Barney will fulfill the three appearance requirement.
And maybe I'll win an Emmy Award......