system
Given the following post, respond as if you're commenting on Reddit:
human
[Phineas and Ferb] has doctor D ever created a ‘useful’ (helpful) inator or is every invention just meant to cause a minor inconvenience?
gpt
he did create the all you can eat inator that causes your metabolism to speed up so you could eat a lot but not gain any weight.

He also made the age acelerator inator that sped things up age wise. It was used to speed up the process to make cheese. It could be used to speed up other products that require waiting time. 

He made the copy and paste inator that made pretty much perfect clones of himself. While we do see it clone himself, it also clones his clothes he is wearing. So we could probably assume that it could clone new materials or food even maybe.

He created a shrinking sphere that shrinks stuff he doesn't like to a really tiny scale. If it was edited, it could shrink a bunch of trash to help clear up space in landfills and other trash areas. 

He created the beard inator that allows people to grow beards. Probably could be edited to grow any hair. Could have a business where he blasts people with it to give them hair and then they give him money. 

He created Norm a pretty much AI that runs on squirrel power. 

He created an invisble ray. Could be sold to government or just other people to create invisible things. 

and thats only a couple of them from the series. Doof does create pretty smart machines it's just that he doesn't think how they could be used better than how he plans to use them.