  We give two different simple proofs for the removable singularities of the
heat equation in $(\Omega\setminus\{x_0\})\times (0,T)$ with $n\ge 3$. We also
give a necessary and sufficient condition for removable singularities of the
heat equation in $(\Omega\setminus\{x_0\})\times (0,T)$ for the case $n=2$.
