A TV appearance by the murderer / murderess?

I liked the fact that both of these episodes were filmed on location at real houses (for the most part) instead of cheesy studio sets. I'm sure that's not the connection, but it's the only thing I can think of right now.

Obvious.
A friend helps cover up the murder by pretending to be the real killer .

Well, not exactly. Nobody pretends to be the real killer in "A Friend in Deed". Hugh Caldwell goes to his friend, Commissioner Halperin, for help to cover up the crime, yes. But Halperin doesn't pretend to be the real killer. He tries to frame Artie Jessup. This is not the same as what Ned Diamond did for Grace Wheeler in "Forgotten Lady". I'm still puzzled as to the connection between the two.

Caldwell did pretend to be the real killer of the DA's wife- he publically dumped the body in the pool.
So, my answer fits even if it's not what you had in mind.

LOL - forgot about that part.

Wild guesses.
Dog is in both eps.
COLUMBO takes a test or is supposed to take a test in both?

I didn't mean to quote you Bruce Marshall. I hit the quote button instead of the reply button.

The connection I was thinking of was that although in many episodes his car is often unreliable, in these two episodes it actually breaks down.