This article is from the Star Trek Tech FAQ, by Joshua Bell inexorabletash@hotmail.com with numerous contributions by others.
Star Trek has "broken" the rules of transporters a number of times.
There are very few glaring examples of misuse of the transporter as a
plot device to save the day, but the worst include:
"Rascals" [TNG] - Picard, Keiko, Guinan and Ro are turned into
children in a freak transporter accident, and later restored. I won't
even try. First off, the biology used in this episode is pure BS.
Secondly, if a quick fix like this can alter the aging process, then
by doing it intentionally, no-one will ever grow old and die again.
Amusing episode, but it gets a thumbs down in the Treknology category.
"Unnatural Selection" [TNG] - The transporter magically rejuvenates
Pulaski. While the mechanism by which her cure works is relatively
sound, the fact that she recovers instantly is anomalous. (See "Man of
The People" [TNG] for a similar insta-heal.) Better to just not ask.
"Tomorrow Is Yesterday" [TOS] - Somehow, the transporter is able to
erase the memories of people by transporting a newer version of
themselves over top of an older version. Talk about saving the day by
transporter abuse!
"The Enemy Within" [TOS] - While I can buy the duplication effect, and
maybe even the two disparate personas of the two Kirks, I think the
recombination of the two was pushing the technology a little bit.
 
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