Apparently, the restaurant in the show "The Bear" is based on Mr. Beef, so we will probably check that out.
I used to go to Mr. Beef a lot and it was very good but haven't been in probably 15 years so can't vouch for it now. Johnnie's is the only place I get beefs. Their sandwiches are a little smaller so I always get two- a combo (beef with the smoked sausage link) and a beef both of them "juicy" dipped in the au jus with hot giardinera. The Turano french bread always hold up and the beef juice adds so much flavor to the sandwich.
If you're doing a dog you probably can't go wrong with Wiener's Circle. The place is a trip with the writings they have on the sign and the girls who swear at you. It's not for everyone and I haven't been in years but they always had really good char dogs with all the Chicago dog fixings. They do boiled too but the char dog is where it's at. The cheddar fries with the Merkt's cheddar were always really good as well but split them, it's a huge portion. They even have a bar now.
Don't remember buying a hot dog in years but the last place I used to get them at is Red Hot Ranch and they do depression era dogs, boiled Vienna beef with just mustard, green relish, onions and sport peppers. I stopped getting the dogs there because they make my favorite cheeseburger in the city. A smash burger with 2 thin house blend patties, American cheese, onions, lettuce, and special sauce. Really simple, half the price and I prefer it to the other pricier burger places.