At the moment, it's not possible to change wake words “Hey Google” and “OK Google” into something else. According to Google, not enough interest has been shown in adding new wake words. That said, a new update might offer a custom wake word option in the future.

Can I change OK Google to Jarvis?

Like Jarvis? You're in right place! Just install the app, give permissions, select hotword and you're done. There's a switch to turn on always on detection which will work even if the device screen is off.

Can you customize the OK Google command?

Despite the many things that Google Assistant can do, it cannot make major changes in its voice-activation command. Google will let you set it to “OK Google” or, on some later devices, “Hey Google.”