Penguin does more of a 'mir' sound.
And since his ear infection/ear wax problem was fixed he now does this noise a lot. When he jumps up, when he jumps down, when he spots one of the other cats, when he drinks from the water bowl, when you go to pet him.
At night he sings....mir, Mir, MIr, MIR, MIRRRRR
It wakes me up most nights.