According to Official Guinness Records,
The largest gathering of people dressed as penguins is 972, achieved by Youngstown State University (USA) at the YSU WATTS Center in Youngstown, Ohio, USA, on 28 October 2017.Youngstown State University decided to attempt a Guinness World Records title because it would coincide with the 50th anniversary of YSU becoming a state/ public university, as well as bring together the time and talents of students, alumni, retirees, current employees and friends of the university.
For a complete list of 2017 records, please visit 2017 Guinness Records in United States.