My Tyranids army are a snake mutation with long tails rather than legs.
http://www.dakkadakka.com/wiki/en/Hive_Fleet_Kielbasa
For the Termagants I made a snake tail and base, I cast a load of them in resin and chopped down the body of the normal model to go on top.
By luck I had one more body than base, and it wasn't worth mixing another lot of resin, so I stuck the body on a base as if emerging from a hole in the ground.
Thus I ended up with 66.6.