In The Greenhouse, No One Can Hear You Scream

Faucaria Tigrina 

They say that life imitates art but perhaps in this case it is the other way around. This is Faucaria tigrina or the Tiger's Jaw - a succulent plant found in South Africa. Yet caught at the right angle the plant does not resemble so much the jaw of a tiger as that of an altogether alien creature, featured in a number of movies starring Sigourney Weaver et al.

The thick, green triangular leaves of the Tiger's Jaw have up to 10 pointed curved teeth along the edges making them look like open jaws. It does not take much of a leap of the imagination to see that there is a certain similarity to the alien. The leaves even form rosettes so you can cultivate a terrifying set of alien creatures in your own home.