Guest Stars Janel Parrish as Mona Vanderwaal Keegan Allen as Toby Cavanaugh Tammin Sursok as Jenna Marshall Torrey DeVitto as Melissa Hastings Brendan Robinson as Lucas Gottesman Charles Hittinger as Sean Ackard Diego Boneta as Alex Santiago Carlson Young as Amber Co Starring Jill Holden as Mrs. Welch Robert Keith Wyatt as Chewy