Critic’s corner

Many Boston sports fans have fond memories of the “Big Bad Bruins’’ of the 1970s. Equally big and equally bad during that decade were the “Broad Street Bullies,’’ a.k.a. the Philadelphia Flyers, a collection of hard-hitting bruisers who beat the Bruins to win the Stanley Cup in 1974 and then won the Cup again in 1975. Now, as the Bruins and Flyers square off once again in the playoffs, the HBO Sports documentary unit takes a look at those 1970s Flyers teams, which were much loved in Philly and much hated everywhere else.

American Idol 8 p.m., Channel 25

The post-Siobhan era begins, with the remaining contestants singing Frank Sinatra songs and Harry Connick Jr. the guest mentor.

Lost 9 p.m., Channel 5

Jack has some questions about what Locke is up to. And we “Lost’’’ viewers have many, many, many questions of our own. Which we know deep down will never be answered.

Frontline 9 p.m., Channel 2

“College, Inc.’’ examines the growth of for-profit colleges such as the University of Phoenix.

Glee 9 p.m., Channel 25

Sue is mortified — as well she should be — by a video of her singing “Physical,’’ the excruciating Olivia Newton-John song. Newton-John herself appears in a cameo. To deliver a long-overdue apology?

Little Chocolatiers 10 p.m., TLC

A chess champion gets a huge chocolate chessboard. And promptly declares chockmate?