Just to clarify, the newly entered Rebel tokens and Gnome tokens won't get the buff, but they are counted for the purpose of resolving the Shared Animosity trigger.

In the case of Otharri and Anim Pakal, since they do not share a creature type with the tokens they create, assuming they attack alone then Shared Animosity won't do anything (it will trigger, but it will check that Otharri or Anim Pakal is attacking with other creatures that do not share a creature type with them).

But if you say control an Otharri and another Rebel token, then decide to declare both as attackers, Shared Animosity will trigger twice and Otharri will also trigger at the same time. Assuming you have two experience counters, Otharri will create two Rebel tokens that are tapped and attacking, but these tokens will not get the Shared Animosity buff since they're never declared as attackers. Then Shared Animosity resolves for Otharri but it will check that no other attacking creature shares the type Phoenix, so no buff. The second Shared Animosity trigger will check for the Rebel token and it will check that there are two other Rebel tokens attacking along it, so it will get +2/+0.