Character actors starting in The Untouchables

Big names? You bet. Robert Redford, Lee Van Cleef, Martin Landau, Rip Torn, Carroll O' Connor, Madlyn Rhue, Ted Knight (!), Edward Asner, Steven Hill. Gavin Mc Leod credits the show with much of his early and continued success in show business. Side note. In the episode "The Masterpiece", watch the intro.
As Les Lampson, "voice" of the series as well as weekend news anchor on non-network-affiliated KTTV in LA, reads off the cast; notice how all the stars make an abrupt head-turn to stage right/screen left...then, when you hear "with special guest star Rip Torn"...HE's looking stage left/screen right.
Probably just an editor having some fun. In "The Frank Nitti Story", as Richard Anderson ("The Six Million Dollar Man") and Myron McCormick ("No Time for Sergeants") walk towards the Chicago office of the "Star Theatre Chain" to peddle Nitti's protection, the camera dollies past the parked cars and stops at the last one as the pair enter the building. Reflected in the car window, you can clearly see the focus puller or grip wearing a festive short-sleeved, loud print shirt and a metal watchband on his forearm. You can also see some electrics on the floor behind as Ness and Dockstone as they leave the Star office. Of course, moments later, the Dockstone character is incinerated when his car explodes in a fireball as he presses the start pedal. Frank Nitti and Louie Campagna (Frank De Kova) sneer with self-satisfied grins, knowing "the Star Circuit" would be buying the mob's protection after all. The scene ends with the obviously dubbed-in voice of a frantic woman, pointing to the burning car and shouting "oooohhhhh...there's a MAN in there!!!" as you see "Dockstone" slumped over the wheel, his lifeless body silhouetted in the roaring flames. Great stuff. Get all you can. There will never be another series like it. Ever.

I just watched one with Gavin McLeod (Murray Slaughter/Capt. Stubbing)as a bad guy.

There's another episode similar to the one with John Banner. It's the Dutch Schultz Story. Marian Ross played Mrs. Schultz and she was the only one in the episode who referred to her husband by his real first name, Arthur. It was just like on Happy Days when her character was the only one who called Fonzie by his real first name which also happened to be Arthur.

The best has to be Elizabeth Montgomery & David White (Samantha Stevens & Larry Tate of Bewitched) playing an ill-fated couple. I couldn't help but think "Darren is not gonna like this...."

Watching one now with Claude Akins, Tim Considine, Joyce Van Patten and Rip Torn

This will be the high point of my day; it's all downhill from here.

I was watching an episode and Ryan O'Neal entered carrying bags as a bell hop. At the end as the credits were rolling I caught a glimpse of the name O'Neal. I backed up, researched IMDB and sure enough the episode was written by his dad, Charles. This was his second appearance on TV and he obviously got the nepotism treatment.

There seems to have been a fair amount of crossover between The Untouchables and The Twilight Zone, too. For example, Warren Stevens and Steve Cochran played gunmen in the episode "90 Proof Dame". Stevens played a (reluctant) mobster in the TZ ep "Dead Man's Shoes" and Cochran played a two-bit thug in "What You Need".

I saw that episode a few weeks ago on MeTV. I laughed my head off.