  One peculiar feature of the solar cycle which is yet to be understood
properly is the frequent occurrence of double peaks (also known as the
Gnevyshev peaks). Not only the double peaks but also multiple peaks and spikes
are often observed in any phase of the cycle. We propose that these peaks and
spikes are generated due to fluctuations in the Babcock-Leighton process (the
poloidal field generation from tilted bipolar magnetic regions). When the polar
field develops, large negative fluctuations in the Babcock-Leighton process can
reduce the net polar field abruptly. As these fluctuations in the polar field
are propagated to the new toroidal field, these can promote double peaks in the
next solar cycle. When fluctuations in the polar field occur outside the solar
maximum, we observe their effects as spikes or dips in the following sunspot
cycle. Using an axisymmetric Babcock-Leighton dynamo model we first demonstrate
this idea. Later, we perform a long simulation by including random scatter in
the poloidal field generation process and successfully reproduce the
double-peaked solar cycles. These results are robust under reasonable changes
in the model parameters as long as the diffusivity is not too larger than
$10^{12}$ cm$^2$s$^{-1}$. Finally, we analyze the observed polar field data to
show a close connection between the short-term fluctuations in the polar field
and the double peaks/spikes in the next cycle. Thereby, this supports our
theoretical idea that the fluctuations in the Babcock-Leighton process can be
responsible for the double peaks/spikes in the observed solar cycle.
