  If x and y are two free semicircular random variables in a non-commutative
probability space (A,E) and have variance one, we call the law of
2^{-1/2}(xy+yx) the tetilla law (and we denote it by T), because of the
similarity between the form of its density and the shape of the tetilla cheese
from Galicia. In this paper, we prove that a unit-variance sequence {F_n} of
multiple Wigner integrals converges in distribution to T if and only if
E[F_n^4]--> E[T^4] and E[F_n^6]--> E[T^6]. This result should be compared with
limit theorems of the same flavor, recently obtained by Kemp, Nourdin, Peccati
& Speicher and Nourdin & Peccati.
