IMO it all started with that numbnutz Gastineau and his stupid sack dance. Then, Billy "White Shoes" Johnson started doing the end zone thing after scoring. Followed by the Fun Bunch, or Smurfs, or whatever they called themselves, with the Redskins who turned it into a regular chorus line
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Doesn't happen as much in college because they have a much stricter "excessive celebration" rule. And of course, college coaches have much better control of their players. Not too many college receivers can tell their coach to eff off after they get flagged, like TO does.