I have seen almost every episode, but i cannot remember to have seen some of the scenes in the intro in any of them.
the scenes i havent seen;
Magica as dragon
sub and kissing shark
one nephew climb away from beagle boy and the mummy running
space ship and money
help?
Magica as a dragon is in a episode, I'm sure, can't remember which one (will check)
Whilst, the others were made for the title sequence and not taken from any episodes.
The only one i can answer for sure is the dragon one. it was from the first season can't think of the episode title, but it was a beagle boy that turned into a dragon, its from the same episode as one of the nephews climbing away from the beagle boy in the intro.
shareScrooge getting electricuted is from 'Armstrong'
Scrooge and nephews walking down staircase is from 'Hotel Strangeduck'
Gyro dressed as a Knight is from 'Sir Gyro de Gearloose '
The Shark scene is from no episode.
The dragon scene is from 'Send in the Clones'
The Mummy is another not from an episode.
The three robots is from 'Robot Robbers'
Scrooge in space is another not from any episode.
Scrooge on the mine cart is from 'Earthquack'
The tiger is not from an episode.
Webby in the lunchbox hamper thing is from 'Dinosaur Ducks'
and Scrooge and Glomgold is from 'Master Of Djinni'
Any other clips are from the Pilot.
Just to add the nephews climbing away from the Beagle's is from 'Send in the Clones' aswell.
In the second season, some new scenes were put into the intro. The ones with Fenton/Gizmoduck are from "Liquid Assets", "Frozen Assets" and "Full Metal Duck".
Intelligence and purity.