Continuity mistake: After Nick falls on the pollen, there's a shot of his mom calling him. Right after, the amount of pollen on him is completely different.
Revealing mistake: When the (green-screened) bee arrives at the flower, the yellow pollen turns dark pink due to the blue/gree screens used.
Revealing mistake: When the green-screened bee passes by Ron and Russ they stare at it, but when it flies away they keep looking at the same spot as before.
Continuity mistake: When Mr. Thompson is shrunk and waves at his family, he is sitting between two bolts. When the angles changes, from a back view, he is sitting right in front of one.
Continuity mistake: When the kids are about to climb the grass, Wayne lets Quark out and the door closes twice: In the close-up and afterwards in the wide angle.
Continuity mistake: Pair of blue jeans disappear from Wayne's shoulder after he turns the faucet off.
Continuity mistake: When Russ falls off the ant, the grass he lands on bounces up revealing the crash mat underneath.
Continuity mistake: When the kids open the waste bag, Nick steps forward, in between two kids, with about 10 centimeters between each. When the angle changes to Amy, Nick is jammed between the kids.
Visible crew/equipment: Stage lights are reflected in Nick's glasses before Russ yells "I say that ant is ours."
Continuity mistake: Nick falls on the pollen on the left side of the flower. When the angle changes he's right on the middle of it.
Continuity mistake: The position of the trash bag left by Wayne differs between shots.
Continuity mistake: When Wayne is destroying the machine, the kids' position differs between the front and back angles.
Continuity mistake: When Wayne tries to shrink the apple, the way he holds the remote control differs between the close-ups and wide angles.
Continuity mistake: When the movie starts and the dog has left the letters, watch the bottles of paint in front of him: They appear closer together in the opposite angle.
Continuity mistake: From Nick's POV, he enters his father's lab and opens the door wide, yet from the opposite angle it is slightly open.
Continuity mistake: When the movie starts, and the dog brings the letters, their position on the table changes between shots.
Visible crew/equipment: When the neighbours visit the Szalinskis to get their baseball and Nick opens the door, you can see the reflection of the cameras and lights in the glass.
Continuity mistake: After all the kids have been shrunk, the nail on the floor swaps from laying between two planks to just one.
Continuity mistake: After the apple explodes, the amount of fruit on Wayne's forehead increases when he sits on the couch and Quark licks him.
Answer: More along the lines of a serious health problem related to her "plumbing".
Greg Dwyer