'Dangerous Nan McGrew' stars Helen Kane and Victor Moore, who also teamed at about this time in 'Heads Up' for the same studio. I can't see any real advantage in teaming these two performers; they have no on-screen chemistry with each other, and (due to the age difference) they couldn't even be teamed as a romantic couple. I've already commented about Kane and Moore in my IMDb review of 'Heads Up', to which I'll add just one detail here. In 'Heads Up', Helen Kane played a character named Betty. Anyone who has seen Helen Kane on screen (or heard her recordings) will see straight away that she was the inspiration for the cartoon character Betty Boop; after seeing 'Heads Up', I now believe that Max Fleischer got the name for his cartoon character from Helen Kane's character's name in that film, plus her habit of scat-singing 'boop-oop-a-doop' syllables into her songs.
In her very few films, Helen Kane usually played supporting roles. 'Dangerous Nan McGrew' is, to my knowledge, her only starring vehicle ... and she proves here that she can't carry a feature-length film. Just a few minutes of her 'boop' routine -- and her incredibly annoying speaking voice -- become very wearying. Here, she's a singer (oh, dear!) in a travelling medicine show run by Victor Moore. She also does an Annie Oakley turn. The medicine act ends up in the Yukon, having dodged sheriffs and process-servers in all the more civilised climes. (The film's title is, of course, a parody of Robert W Service's Yukon epic 'Dangerous DAN McGrew'.) The saxophonist in the medical show is Stu Erwin, giving perhaps the most annoying performance of his career.
Up in the Klondike, Kane and Moore cross paths with bank robber Foster, although it's not clear why a bank robber would be up here in the frozen tundra where the only banks are snowbanks (boom, boom!). With frozen assets (ba-dum-bum!). Those jokes are about as bad as the ones in this movie. The bank robber is played by Frank Morgan, who spent the first half of his career playing mean villains and the second half playing whinnying dimwits. He was more credible as mean villains, as he's cast here.
This movie is largely incoherent. We're told that one of the members of the medicine show is a fugitive, on the run from a murder charge, but we're not told (until nearly the end) which one: this is a cheap ploy to inject some suspense. Handsome James Hall shows up in a Mountie uniform, looking for someone to arrest. All these people stranded in the Klondike decide to have an ice carnival(!), the centrepiece of which is a costume party. Helen Kane shows up at the party dressed as a little girl ... and that's where my blood sugar went out of control. In her normal mode, Helen Kane's boop-a-doop antics had her acting very little-girlish, but she was still clearly an adult woman. Here, kitted out as a four-year-old (but still plainly an adult), Kane's little-girl act just becomes unbearable.
Meanwhile, at the same party, tough-guy villain Frank Morgan shows up dressed as Buster Brown, complete with Dutch-boy wig and short trousers. The sight of this particular grown man disguised as a five-year-old boy is bad enough, but the effect is made even more ludicrous because Morgan has kept his moustache. Why (you ask) would this macho villain humiliate himself like this? Well, erm, the plot of the movie involves a robbery in which the henchmen have been told to hand the swag to a guy disguised as Buster Brown. Maybe he didn't want to look conspicuous...
'Dangerous Nan McGrew' is directed by Mal St Clair, a name well-known to aficionados of old-time film comedy ... but not for favourable reasons. St Clair worked with an impressive list of comedians and comic actors, yet he almost invariably directed their very worst films. Mal St Clair doesn't deserve all the blame for the failure of 'Dangerous Nan McGrew', but he certainly deserves some of it. I'll rate this slush fest 2 points out of 10.