From the comics: Why didn't the mask work on Walter?
It's explained that it's because he is immune to cartoon attacks and also because his face is too big (though it worked on a monster in one of the cartoon episodes) so the Mask can't work on him. It's like if people don't believe in illusions, illusionary attacks can't hurt them.
Everyone (the cops especially) seems to give a rather mundane interest to the Mask's cartoonish abilities. He zips around the bank at superspeed, freezes himself in midair, and ejects his own eyes and skull while screaming in terror. Nobody gives this much of a reaction.
Perhaps it's part of the Mask's powers, like how he got the police force to do a song-and-dance number with him.
When Tina leaves the police station after visiting Stanley, she sees some of Dorian's gang come for her. Why not just run back into the police station and explain she's in danger? I'm sure the detective wouldn't mind giving her protection in exchange for information on Dorian and his gang.
Uh-huh... And if Dorian finds out she went to the police, he could make her life ten times worse.
In addition, if they find out she's the girlfriend of a man in organized crime, at best she'll be interrogated and at worst tried as an accessory to Dorian's crimes (she did help him spy on the bank during her first meeting with Stanley).
Plus, there may be a cop or two that's under Dorian's payroll.
So, Kellaway finds out that Stanley is the Mask because of his fingerprints? A magical mask that turns you into a Reality Warper leaves your fingerprints totally unchanged?
Aside from making him indestructible and turning his head green, the Mask doesn't appear to change anything about Stanley's physical body. It probably could change your finger prints if you willed it to, but Stanley wasn't thinking about that at the time.
We're assuming this is the case. We're assuming that the fingerprints found at the bank were due to the robbery, and not because Stanley worked there. Kellaway doesn't display much in the way of actual detective skill, instead wanting to go after the first suspect he can, and even when Doyle calls the bank robbery strange, Kellaway ignores it. He leaps to the logic that Stanley is the Mask without question because a tiny scrap of cloth found at a nightclub matches the pajamas - which may be a connection, but the club was packed full of people. Then he ignores all these superpowers, doesn't care that the cheap rubber mask isn't a match to the Mask's face when Stanley is dumped at his feet, doesn't go after the people who gave him Stanley for dumping a bound man out of a moving car.
The cartoon later said they have different fingerprints, which doesn't totally retcon the movie when you think about it. Then again, in one of the original comics, a teenager wearing the Mask changes his fingerprints to animal stamps so it is an option.
Why did The Mask need to rob a bank? He can create objects out of nothing couldn't he just create all the money he wants?
The objects he creates probably don't have much permanence. Also, Stanley hated working there, so it was also to spite the bank itself.
He didn't need to. He just did it For the Lulz. The Mask feeds on Stanley's repressed desires, and it is not a stretch that he fantasized of robbing the bank at one point.
How did Kellaway conclude that Stanley was The Mask with a green-eared rubber mask when The Mask has no ears?
Who said anything about any ears?
You have to remember something vitally important: The characters are not watching the movie. They aren't seeing all the detail as clearly as we are, and they're not getting an exact replay afterward. He saw the Mask had a green head, so a green mask that looks close enough is, well, close enough. He's not getting every detail, and he's not going to throw the whole thing out because of one inconsequential one when he's got a mountain of reasons to believe Ipkiss is The Mask.
The green rubber mask is merely the last straw for him. We're meant to assume that Stanley stuck out like a sore thumb as he tried to run after the Cuban Pete number (in fact, a junior novelization confirms this).
When placed onto or close enough to the face, the said artifact wraps itself around the user's head by producing small tentacles from its edges covering the head completely. Meanwhile the face itself presses itself to the user's face, namely around the eyes, nose and mouth. Then it begins to squeeze the face and head all the while distorting and deforming it. This leads the eyes to enlarge and bulge out while also affecting the teeth, and this causes distressing pain in the face and head. This also begs another question.
How does the Mask itself adhere to the user's face and head during use?
The Mask only works at night, so it could be made of an entirely different substance all together.
Even so, the object in question appears to be wooden when not in use, but it seems to turn into rubber or something of the sort when it is in use.
The two times we see Stanley removing it, his skin stretches only to bounce back to normal. This can mean two things. Either the inside of the Mask turns into some type of adhesive. Or, it produces a suction seal similar to that of a vacuum cleaner.
How on earth does Calloway connect Stanley to the robbery in the first place? I mean let's walk through his logic for a minute. He knows that Dorian Tyrell's people were part of a botched bank robbery and shootout. He's got them dead to rights on that due to the corpse in Tyrell's office. And then, on the floor of the high end night club below that office - which just hosted at least a few dozen legitimate customers - he spies a scrap of fabric...which he immediately identifies as a scrap of Stanley's Pajamas, and because of this he concludes that Stanley must have been the unidentified robber in the mask. To repeat...he somehow concludes that it makes perfect sense for Stanley Ipkis to be at the Coco Bongo in his pajamas, and that because he was in the Coco Bongo in his pajamas (alongside the other more formally dressed patrons), he must have been at the robbery across town...as the unidentified robber they have on camera in a yellow zoot suit. ...Seriously, what?
More that you have two sites nominally linked only by Dorian and The Mask, and suddenly you have a piece of evidence that ties Stanley's pajamas into the mix. Logically, the only way Stanley's pajamas — which were too tacky not to be noticed — could have been there was if Stanley was wearing them. Stanley, who happens to be an employee of the bank that Dorian and his men failed to rob. Kellaway's a jerk, but he did a good job of following the evidence.