Complex sentence: Accord to at least one source, the pupu platter was probably first introduced to restaurants on the United States mainland in 1934 by Don the Beachcomber and became a standard at most Polynesian themed restaurants such as Don's and at Trader Vic's.
Split into simpler sentences: Accord to at least one source, the pupu platter was probably first introduced to restaurants on the United States mainland by Don the Beachcomber in 1934. It has since became a standard at most Polynesian themed restaurants such as Don's and at Trader Vic's.