Mobilizer Mech
Artifact — Vehicle
Flying
Whenever this Vehicle becomes crewed, up to one other target Vehicle you control becomes an artifact creature until end of turn.
Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.)
Jonathan Kuo
Rulings
That ability doesn't count as "crewing" a Vehicle for any ability that would trigger off of a Vehicle becoming crewed.
(wotc • 2022-02-18)
If an effect that causes a Vehicle to become a creature doesn't specify its power and toughness, it has the same power and toughness that it would normally have if it were crewed.
(wotc • 2022-02-18)
Mobilizer Mech's second ability triggers whenever its crew ability resolves, even if it is already a creature at that time.
(wotc • 2022-02-18)
Rulings
That ability doesn't count as "crewing" a Vehicle for any ability that would trigger off of a Vehicle becoming crewed.
(wotc • 2022-02-18)
If an effect that causes a Vehicle to become a creature doesn't specify its power and toughness, it has the same power and toughness that it would normally have if it were crewed.
(wotc • 2022-02-18)
Mobilizer Mech's second ability triggers whenever its crew ability resolves, even if it is already a creature at that time.
(wotc • 2022-02-18)