8 p.m. on 6, ‘‘How I Met Your Mother’’ — A small galaxy of Canadian celebrities, including Alan Thicke, Alex Trebek and Geddy Lee — is on hand for this new episode, in which Barney (Neil Patrick Harris) discovers a lost episode of Robin’s (Cobie Smulders) TV show ‘‘Underneath the Tunes’’ from her days as Canadian pop star Robin Sparkles. Lily and Marshall (Alyson Hannigan, Jason Segel) think that Ted’s (Josh Radnor) new girlfriend (Abby Elliot) might be a stalker in ‘‘P.S. I Love You.’’
9 p.m. on A&E, ‘‘Hoarders’’ — Fuzzie and Fred are middle-aged former punk rockers who still live like teenagers, filling their home with records, toys, mannequins, masks and other items and relying on Fuzzie’s hard-working father for support. The gravy train is about to come to a stop, however. Also in this new episode, the organizers work with Nancy, whose home is such a disaster that her niece fears she’ll die in there.
10 p.m. on TNT, ‘‘Monday Mornings’’ — From famed TV giant David E. Kelley (‘‘Boston Legal’’) comes this witty new hospital drama based on the novel by CNN chief medical correspondent Dr. Sanjay Gupta. The title comes from the weekly meetings where the doctors’ methods are scrutinized to find out whether they did the right thing in matters of life and death. The cast includes Jamie Bamber (‘‘Battlestar Galactica’’), Alfred Molina, Ving Rhames and Jennifer Finnigan.