Dino Smurf
DINO EGGS (1983) was also known to many as DINO SMURF. In fact, more than one post on retro game sites has expressed surprise that DINO SMURF was ever anything *other* than DINO SMURF.
DINO SMURF -- a widely-distributed parody of DINO EGGS (and of course Smurfs) -- was the first part of a planned trilogy of hacked games by Dead Smurf Software (Andrew Johnson and Preston Nevins). Castle Smurfenstein (Castle Wolfenstein) was the second part of the trilogy. In DINO SMURF, Time Master Tim became Smurf Butcher Bob, as he tried to save his children by going back in time and destroying the smurf's prehistoric ancestors (including the now extinct orange smurfs).
Thus, we believe DINO EGGS/SMURF to be one of the first -- if not THE first -- game "mod" ever distributed.
More about the Dead Smurf Software Trilogy is posted here...