
I drew a picture of what I think is a chubby, cute Alien facehugger, then tried to crochet it for a bag charm (or keychain, brooch, magnet - haven't decided yet). Success!
This was totally easy. I've written out general instructions so that you can change the size of the facehugger.
For the body:
crochet a circle.
Make an air bag by making a crocheted scallop. This is how I did it: in any stitch, sc. In the next stitch: hdc, 2 dc, hdc. In the next stitch, sc.
For the legs: slip stitch to where you want the first leg to be. ch 4, turn, and slip stich back to the body. Slip stich to the next stitch, and repeat. Remember to leave a space between legs 4 and 5. Make 8 legs total.
Make another air bag.
Make the tail: ch 12. Turn. sc, sc decrease, sc, sc decrease, etc., until you get back to the body. This will make the tail curl. Fasten off and weave the yarn tail into the back.
Optional:
I made another crocheted circle to sew to the underside, so that I could add a little scrap-yarn stuffing for a slightly puffy bag charm.
P.S. Here's a
link to another Craftster's project: a full-sized knitted facehugger!
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ETA:
Another facehugger, more like the ones in the movies.

Here, doggy, doggy.

Inevitable.

Awww, Alien drone has a little dolly.

For this second one, I modified the pattern by adding
longer legs and a longer
tail. Also, there's
an extra round for the air bags - it's the same sequence of stitches, just piled on top of each other. I originally did one round for the airbags, but after doing the legs, the air bags looked small, so I added the second round.
It was big enough to need more shaping, so I added a
top piece:
Ch 12. Turn.
In first stitch, sc, 2 hdc, sc. In the top loops only, dc to the second last stitch.
sc, 2 hdc, sc in the last stitch. Do not turn (just rotate the piece).
In the "bottom loop" only (i.e. the other half of the loop that you haven't crocheted into yet), dc to the end and sl-st to join with the first stitch.
Stuff lightly, and sew this piece to the top of the facehugger.