Speedbump has miraculously survived ninety-nine rocket crashes, and he's aiming for an even hundred.

Afterburner Expert

Exhaust — {2}{G}{G}: Put two +1/+1 counters on this creature. (Activate each exhaust ability only once.)
Whenever you activate an exhaust ability, return this card from your graveyard to the battlefield.

Aetherdrift Promos

Aetherdrift

Exhaust — {2}{G}{G}: Put two +1/+1 counters on this creature.
Whenever you activate an exhaust ability, return this card from your graveyard to the battlefield.

Exhaust abilities can be activated any time you could normally activate an ability.

If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.

If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.