You may get just one Etali set off.
Deadpool’s means is a alternative impact that modifies how he enters the battlefield:
614.1c Results that learn “[This permanent] enters with . . . ,” “As [this permanent] enters . . . ,” or “[This permanent] enters as . . . “ are alternative results.
Your 3 Deadpools enter on the similar time as a result of they’re created by a single impact. If you select one other creature to swap textboxes with, it’s important to select one which was already on the battlefield earlier than the tokens have been created. That is true for all 3 tokens, and there are both none of these tokens on the battlefield, or all 3 of them, so you can not select one other token to swap with.
614.12. Some alternative results modify how a everlasting enters the battlefield. (See guidelines 614.1c–d.) [..]
614.12a If a alternative impact that modifies how a everlasting enters the battlefield requires a alternative, that alternative is made earlier than the everlasting enters the battlefield.
If it was potential to “daisy-chain” the alternative impact as you steered, it might imply that there’s a time when just one Deadpool token exists in order that the second can swap with it (can solely swap with a creature everlasting), then two so the third can swap with it, and solely then the third would exist.
Nevertheless, that might contradict the truth that, for instance, if 2 Apothecary Geist enter on the similar time, they see one another and each set off, so there is no such thing as a time when one of many Geists could be the one Spirit on the battlefield:
603.6a Enters-the-battlefield skills set off when a everlasting enters the battlefield. These are written, “When [this object] enters, . . . “ or “At any time when a [type] enters, . . .” Every time an occasion places a number of permanents onto the battlefield, all permanents on the battlefield (together with the newcomers) are checked for any enters-the-battlefield triggers that match the occasion.
Accordingly, there exist both 3 Deadpool tokens or none. That implies that one of many tokens can swap its innate textbox with the Etali textbox from the unique Deadpool, and the opposite two tokens can solely get one other, equivalent Deadpool textbox, and you’ll get one Etali set off your 3 Deadpool tokens.
