While The Three Stooges and the rich investor couple are being sprayed with whipped cream, the fountain pen flies off and hits Larry in the forehead. Two shots later, the pen is back on the eggbeater while it's on fire.
After getting sprayed by the rain cloud, Shemp says "Gee whiz!", but his mouth does not move.
The hat Shemp supposedly levitates--visibly attached to a string--does not move in sync with his gestures.
When the rain cloud sprays Shemp with water, the hole where the water comes from can be seen (with another hole above it).