Lil Delirium can transform into the same familiar multiple times in a row and therefore stay in the same form for more than 10 seconds.
Every time Lil Delirium transforms from a free-floating familiar to a follower one, it positions itself at the end of the familiar train.
Lil Delirium can damage Isaac when transformed into BBF or Bob's Brain.
Familiars that follow behind Isaac have a certain priority in how close their position is to him over other familiars. Lil Delirium starts at 4th / 6th priority regardless of the familiar it transforms into as long as it starts as a familiar that follows behind Isaac. When Lil Delirium changes out of a familiar that follows behind Isaac; its priority resets and becomes equal to its next form (e.g. having 2nd / 3rd priority when its next form is ). Changing from one following familiar to another will not change priorities.
This item belongs to the Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.Error: The given transformation ("conjoined") does not exist.
Synergies
Box of Friends: The copy of Lil Delirium will be a different random familiar.
Tainted Lilith + Birthright: Lil' Delirium will only stack on top of Gello if it transforms into a familiar that does.
Lil Delirium is one of only five items to appear in both the Angel and Devil item pools, the others being 7 Seals, Void, Duality, and Purgatory.
Bugs
Bug!
When entering a new floor or room, Lil Delirium and a normal familiar you have can swap forms as long as Lil Delirium is currently transformed as that familiar. For example, if you have Lil Brimstone and Lil Delirium, Lil Brimstone will become Lil Delirium's form, while Lil Delirium will look normal. This persists for the other familiar, but Lil Delirium will go back to normal. This also works if you pick up the familiar Lil Delirium is transformed as.[Check ingame]
Delirium.
Familiars that follow behind Isaac have a certain priority in how close their position is to him over other familiars. Lil Delirium starts at 
4th / 
6th priority regardless of the familiar it transforms into as long as it starts as a familiar that follows behind Isaac. When Lil Delirium changes out of a familiar that follows behind Isaac; its priority resets and becomes equal to its next form (e.g. having 
). Changing from one following familiar to another will not change priorities.
Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.Error: The given transformation ("conjoined") does not exist.
Box of Friends: The copy of Lil Delirium will be a different random familiar.
Tainted Lilith + 
Birthright: Lil' Delirium will only stack on top of Gello if it transforms into a familiar that does.
7 Seals, 
Void, 
Duality, and 
Purgatory.
Bug!
Lil Brimstone and Lil Delirium, Lil Brimstone will become Lil Delirium's form, while Lil Delirium will look normal. This persists for the other familiar, but Lil Delirium will go back to normal. This also works if you pick up the familiar Lil Delirium is transformed as.[Check ingame]
Delirium Unlocks 
The Binding of Isaac: Rebirth
