All health will be lost when changing into The Lost. Changing from The Lost to any other character will leave them with a half Soul Heart.
Keeper will always start with 2 Coin Heart containers. Bone and Half Soul/Black Hearts will be rounded up to 1 or 2 filled coins. Red Hearts are not rounded which allows him to have half Coin Hearts. Changing from Keeper to any other character will turn his Coin Hearts into Red Hearts.
All Red Heart containers are converted to Coin Heart containers when transforming into Keeper, with a minimum of 2 and up to a maximum of 3. Only red hearts will determine if the coin heart containers are filled or not, and Soul/Black hearts will be converted into blue flies. One coin heart container will be filled if he would otherwise have no health. Changing from Keeper to any other character will turn his Coin Hearts into Red Hearts.
Changing into The Forgotten will not affect The Soul's health. Red Hearts are converted into Bone Hearts. Soul/Black Hearts will be lost. He will gain an empty Bone Heart if he would otherwise have no health.
All soul hearts will be converted to soul charges when changing into Bethany. She will gain one full Red Heart container if she would otherwise have no health. Changing from Bethany to any other character will convert her soul charges into soul hearts.
Heart Containers will be divided evenly and split up when changing into Jacob and Esau. Changing from Jacob and Esau to any other character will leave them with Jacob and Esau's combined health.
Activating Clicker typically only consumes passive items, but with Schoolbag it can consume the item in the other activated item slot if that item was the most recently collected.
Tainted Cain can craft the Clicker and other useful items and then use Clicker to change characters. In this way, runs started as Tainted Cain can be useful to complete other character's completion marks, even when Tainted Cain's own completion marks are finished. Although Clicker will only turn tainted characters into other tainted characters, Tainted Cain can also craft Lazarus' Rags and die to become a non-tainted character and could then use the Clicker to change into other non-tainted characters.
Car Battery: Isaac will transform twice and have the last two picked up items removed.
Rock Bottom: Stat upgrades given by removed items are retained, and the best stats of each character you turn into are retained, possibly creating some powerful characters, like Tainted Keeper with all the Berserk stats of Tainted Samson.
Switch PW44 Y9WH (Treasure Room at spawn in Normal mode, go south in Hard mode)
If Lazarus dies, becomes Lazarus Risen, and then uses Clicker to become another character, the character will have Lazarus' hair and freckles. This also works with reviving items such as Ankh.
If Clicker is used in The Soul form of The Forgotten, it is possible to be turned into another Forgotten. Both Forgottens have independent health bars and can be swapped between, but no Soul form exists anymore. Turning into any other character does not cause the bug.
If Clicker turns the player into Tainted Lazarus, he will not alternate between his normal form and Dead Tainted Lazarus after a room clear or after using Flip. Saving and exiting and re-entering the game will return Tainted Lazarus to normal.
If Clicker turns the player into Jacob and Esau, after collecting Eden's Blessing previously in the run, any items that would have been normally gained at the beginning of the next run, are instead given to Jacob and Esau instantly. This makes it so that no free random items are gained at the start of the next run.
If Clicker turns the player into Dead Tainted Lazarus, the character will flip back and forth to Tainted Lazarus like normal, but Dead Tainted Lazarus will hold all of the previously held items. If Tainted Lazarus collects any items and then Clicker is used to become another character, those items are not transferred to the new character (only the items held by Dead Tainted Lazarus). If you have the option to show collected items in the HUD, this section is still split showing Tainted Lazarus's collected items even though they are not applied to the current character.
Switching into The Forgotten can sometimes give him a half Soul Heart along with Bone Hearts.
Switching into Tainted Isaac crashes the game. While it's possible to continue from the last save/autosave, the Clicker order is predetermined, so using it again will cause the same crash.
Switching into Tainted Forgotten does not spawn Tainted Soul, leaving the player unable to move. Softlocking the run can be avoided if you can use the Clicker again (such as a 48 Hour Energy pill or by having started with a double charge from The Battery)
Using Clicker when the last collected item is a gulped trinket crashes the game.
Using the Clicker to become Tainted Jacob does not cause Dark Esau to spawn for the current floor. Dark Esau will spawn as normal on the next floor.