The Mind Is a Plaything of the Body/Playing With

Basic Trope: For some reason after shapeshifting the way you think is different.
 * Straight: Bob and Alice have their minds exchanged by a Mad Scientist. Despite some initial confusion and discomfort, they rapidly adjust to their new bodies. After a month or two, even though they remember their old lives, you would not be able to tell from their mannerisms or emotional reactions that they'd ever been the opposite gender.
 * Exaggerated: Bob has the ability to turn into a wolf, gaining the instincts of that form. But after a week in that form, he forgets he was ever human.
 * Downplayed: A character's sexual orientation changes after a gender bender, but not their behavior or personality.
 * Justified: The new body's hormones and outside social pressure to conform to the new shape's role combine to affect the shifter's attitudes.
 * Or the magic in a Baleful Polymorph curse slowly erodes the victim's memories and personality to make it ever harder for them to seek out or accept a cure.
 * Or the shapeshiftee is presented with a second consciousness that begins to blend with his own.
 * Inverted: The Body Is A Plaything Of The Mind. Whatever body Emperor Evulz possesses slowly changes over time to look like his original form; his personality is just that strong.
 * Alternatively: Whenever Bob experiences Character Development, his appearance alters as a result.
 * Bob's personality is like the Animal Stereotype of a wolf, so a certain magic spell turns him into a wolf.
 * Subverted: Bob has been acting more and more like a normal dog since he shifted into that form--but it's actually an put-on so that the villain will feel free to speak in front of him and spill his plans.
 * Double Subverted: Once the villain has been sent to jail, Bob is told that he can turn back now, but he refuses, because being a dog is more comfortable for him now.
 * Parodied: Macho action hero Bob is turned into a woman. He immediately begins acting out the most demeaning feminine stereotypes and insists that his name is now Missy. Several other characters point out that the Applied Phlebotinum involved doesn't affect the victim's personality...Missy doesn't believe them. "My new lady parts compel me to enjoy shopping for frilly lingerie!"
 * Alice dyes her hair to a shade similar to Bob's, and immediately starts acting like Bob.
 * Deconstructed: The horrific nature of the personality changes in the new body are played up. The victim's slow, inevitable Loss of Identity, and the reactions of those around the victim as the person they knew slips away to be replaced by a stranger.
 * Reconstructed: The victim had very little that cared about him prior to the transformation in the first place, and he misses the old life as little as it misses him. Loss of Identity might still happen and is still scary, but the victim still sees it as a step up and the Nightmare Fuel is deadened.
 * Zig Zagged: Bob has been acting more and more like a normal dog since he shifted into that shape, but it was an act to throw the villain off guard, but Bob doesn't change back once the villain is captured, but he retains mostly human mannerisms, but then he becomes leader of a pack of feral dogs and renounces his humanity, but....
 * Averted: The rules of magic in this universe state that the body, mind and soul of a person are separate targets for transformation spells. Any behavioral changes in a physically transformed person are purely down to actual experiences in the new body.
 * Enforced: First Law of Gender Bending.
 * The shapeshifting ability gives the shifter the instincts of the new form as a safety feature to keep them from dying.
 * Lampshaded: "Don't be silly! Turning into a dog doesn't affec--Squirrel!"
 * Invoked: Helga the Hot includes a personality-eroding effect in her Baleful Polymorph spells to really screw her victims over.
 * Defied: "This amulet I wear prevents me from losing my true self, no matter my current form."
 * Discussed: "Bob's been acting kind of...funny ever since he turned into a dog, don't you think?""
 * Conversed: "Given that Fanfic Writer X always has her Gender Bender victims totally embrace their femininity by the end of the story, regardless of their original personalities, I'm going to presume Author Appeal."
 * Played For Laughs: Bob retains personality traits of shapes he's shifted into for a few minutes after returning to human, but it's just a set-up for episode-ending jokes.
 * Played For Drama: Bob's tendency to become more deeply immersed in the personality of his alternate forms is a serious problem, and suspense is built in long storylines as to whether or not he'll be able to change back in time.

I could go Back to The Mind Is a Plaything of the Body, but I like my new life as the footer on this page better.