In Erikas New Perfume regressing Heather and progressing Sarah their clothes changed to fit their appearances. Only partially played straight for Heather because while her clothes do change to fit her new size, she does not get training pants out of it as her sister soon mentions.
Earlier than either of these, this is averted for Erika. Her needs in clothing (particularly underwear) change after she uses the perfume, but she keeps the same ones that according to the way everyone now remembers she's never supposed to have had.
Averted in Small Problem, when Debby wakes up to find that she had shrunk out of her pajamas.
Averted in the Whateley Universe by Shifters. Either they're not very good, and they lose their clothes, or they're so good that — like Jimmy T — they fake their own clothes as part of their appearance.
The 'Hulk' problem is parodied in the story "Tales of the MCO", when one of the commercial breaks for the program the students are watching is for the upcoming Merchant-Ivory film "Hulk 1809", which includes in the trailer a Keira Knightley look-alike saying to the hero, "Good sirrah, where are your clothes? And why are your pants that hideous shade of purple?"
Morduval from Tales from My D&D Campaign transforms briefly into a large tentacle monster whenever he's attacked, bursting out of his clothes, but always changes right back, leaving him naked (except for a Censor Box ). It turns out his outfit is self-regenerating, growing back after about 20 seconds, but this means that he's an aversion to the trope, even though he has literal magic pants!