When Sandy comes over and surprises Dorothy in her apartment, she takes her coat off twice.
Julie throws the flowers that Dorothy gives her on the table twice.
When Julie and Dorothy are talking in Julie's kitchen, Julie's trousers change twice.
At the party, when Michael (out of drag) meets Julie and lays "the line" on her, she throws a drink in his face. The drink hits the back of the man behind them. The man jumps but doesn't turn around. When Michael turns to dry his face on the man's coat, the coat is dry, and Julie's glass still has champagne in it.
When Dorothy and Julie are practicing their lines, her baby is sitting near her facing Dorothy in one shot, but then the camera goes to Dorothy and snaps back and the baby is facing in the other direction.
Sandy tells Michael to take Vitamin C "with milk only."
Vitamin C should never be taken with milk, other dairy products, calcium supplements, or antacids that contain calcium. Calcium may make it harder for your body to absorb certain minerals.
"Dorothy Michaels" does not exist and therefore would not have a Social Security number. No television production company would hire anyone unless they or their agent provided one, and using a false Social Security number is not only a very serious offense it is easily detectable.
Sandy pockets some grapes and says that her dog "likes grapes". However, grapes and, in particular, raisins are very toxic to dogs and cats, so if she had ever fed her dog grapes before, it would no longer be alive.
The airborne panning view of midtown Manhattan (a transition shot after the montage of Dorothy's magazine photo-shoots, filmed above Union Square) is stock footage from the early 1970s or perhaps earlier; at least one skyscraper completed by 1975 is missing (the One UN Plaza towers).
In the beginning of the movie, when Michael is auditioning for a part in various shows, the speaking voice of the director is exactly the same for each play.
Even before he begins to play the character of Tootsie, Dustin Hoffman's eyebrows have obviously already been plucked into a more feminine shape.
When Dorothy is in Julie's flat trying to calm the wailing child by holding her in his arms and running around in circles, the baby actually isn't crying at all.
Once the Tootsie character became nationally famous, the mass media would certainly have dug into her non-existent past to determine when and where she was born, where she grew up and went to school, who her parents and friends were, etc. Tootsie would have been exposed as a fraud almost immediately.
When Michael (as Dorothy) is running lines with Julie at Julie's apartment and asks her why she drinks so much, Julie says, "Because it isn't fattening, and it's bad for me". Any professional actress watching her weight/concerned about her appearance would know all too well that alcohol is both very fattening and causes a bloated appearance.
Michael is surprised that he has to share a room with Julie when they are visiting Julie's father. But he brought along a wig with curlers supposedly to give the impression that Dorothy sleeps in her curlers. There would be no reason for going through that trouble if he thought he was sleeping in a separate room.
When Michael Dorsey is teaching his students in the opening title, he tells them it is important to take the job and that unemployment is there and they will be on it if they don't get a job. In the next scene, and many other scenes later he walks away from work because of idiotic opinions about how to perform a character, which is a contradiction of the character.