  We report the discovery of two new types of variability in the neutron star
low-mass X-ray binary MXB 1730-335 (the 'Rapid Burster'). In one observation in
1999, it exhibits a large-amplitude quasi-periodic oscillation with a period of
about 7 min. In another observation in 2008, it exhibits two 4-min long 75 per
cent deep dips 44 min apart. These two kinds of variability are very similar to
the so-called $\rho$ or 'heartbeat' variability and the $\theta$ variability,
respectively, seen in the black hole low-mass X-ray binaries GRS 1915+105 and
IGR J17091-3624. This shows that these types of behavior are unrelated to a
black hole nature of the accretor. Our findings also show that these kinds of
behaviour need not take place at near-Eddington accretion rates. We speculate
that they may rather be related to the presence of a relatively wide orbit with
an orbital period in excess of a few days and about the relation between these
instabilities and the type II bursts.
