Keeper is not able to walk through doors or into Crawl Space, although he is able to enter the beam of light that takes Isaac to the next floor after the Mom's Heart / It Lives fight, the one spawned by Genesis, as well as entering the big chest after defeating bosses in later stages.
Respawn items work as normal for Keeper. (see Interactions)
Similar to Jacob and Esau, it is possible to take both items between item choice pedestals with careful positioning.
Even though Keeper is considered a second character, the run ends if Isaac dies.
Technically, Strawman is marked as a familiar item in the game's files, although most familiar-modifying items, such as BFFS! don't have any effect on Keeper.
Unlike Jacob and Esau, invincibility frames are not shared between Keeper and Isaac.
If collected in a challenge where Isaac is blindfolded, Keeper will be blindfolded too.
Re-emerging from the part of Mines II where Knife Piece 2 is hidden will cause Strawman to be regenerated from scratch. This permanently remove all items the summoned Keeper had collected up until that point.
If Strawman is picked up during the second lap of a Victory Lap, he will become The Lost alongside Isaac on every subsequent lap.
Birthright: If Keeper is the one picking it up, it will grant him a heart container.
Crooked Penny / Diplopia: Picking up multiple copies of the item will spawn additional Keepers that each have their own inventory.
The Polaroid / The Negative: Keeper can take the other photo not chosen by Isaac. Keeper will not directly benefit from holding the Polaroid, but the Negative will give him a damage up. Keeper can use his photo to open A Strange Door, allowing Isaac to keep his. If intending to go to Chest or Dark Room, note that the photo held by Keeper will be lost if he dies.
Sanguine Bond: A very beneficial item for both Isaac and Keeper, as it is fairly easy to snowball into infinitely playing the spikes.
Yum Heart: Because of how Yum Heart works in co-op, when Isaac uses Yum Heart, it will also restore one coin heart for Keeper.
Esau Jr.: Switching once and back will clear any items Keeper may have had.
False PHD / PHD: Identifies pills, but doesn't convert them.
Genesis: Will not grant item choices for any of Keeper's collected items.
Lachryphagy: Isaac's tears can feed Keeper's for great damage. If Isaac, however, has Lachryphagy, Keeper's tears still interact with them, although sometimes it feeds them, other times it absorbs them, without the splitting effect.
The Ladder: A ladder will spawn across gaps for the Keeper, however he cannot use it, only Isaac.
Spirit Shackles: The effect will only happen once, as Keeper cannot recharge them.
Tainted Cain: Items will not turn into pickups if Keeper takes them.
A "straw man" (sometimes written as strawman) is a form of argument and an informal fallacy of having the impression of refuting an argument, whereas the real subject of the argument was not addressed or refuted, but instead replaced with a false one. One who engages in this fallacy is said to be "attacking a straw man".
Strawman, alongside Mom's Ring, are one of two items which cannot be rerolled into by Spindown Dice; in Strawman's case, this is because the next item by ID number is Dad's Note, which cannot be rerolled by any means.
If Keeper picks up Missing No., Strawman will not be removed from Isaac's inventory when Keeper dies and Keeper will not spawn spiders. Keeper will then respawn with no items upon picking up any familiar.