Donatello, the Brains

The additional Mutagen token won't have any abilities the other tokens were created with. Anything else specified in the effect creating the token (such as tapped or "Exile that token at end of combat") applies to both the original tokens and the Mutagen token.

You can have two commanders if each one has "Partner—Character select." You can't mix and match them with cards that have other partner abilities.

Some spells and abilities that create Mutagen tokens require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. The Mutagen token won't be created.