When I summon a squid with the invisibility effect, and then use a spawnegg to summon a Guardian, the Guardian will target the squid as if it were visible.
(Which is usefull when trying to keep track of invisible squids, but probably not intentional)

Noteworthy: My squids also had the "PersistenceRequired" and the "Invincible" tag set to 1

/summon Squid 1470 95 -627 {PersistenceRequired:1,Invincible:1,ActiveEffects:[

]}