The Phillips portable DVD player has -- for some unknown reason -- an
old-fashioned plug (equal-sized prongs). It is plugged into a
UL-approved "temporary power tap" that has the uneven-sized
receptacles, with one slot larger than the other. The strip has three
prongs and the wall has a three-prong receptacle.

Is it dangerous to plug the old-fashioned prongs into the modern
receptacle with the uneven slots? There are no other pieces of
equipment involved, just the DVD player.