Here's a Theory: In the "Tom and Jerry Kids" show, it was stated that Tom is an orphan. Thus we do not know his true origins. Also we see in that show that even from his early years and through all his life, Tom has suffered and endured damage that should had killed him many times over; yet he keeps coming back. Now, the saiyan race is known for becoming stronger after surviving near fatal wounds (known as zenkai boost). Given how Tom keeps surviving more and more ridiculous stuff over the years, it's not impossible to conclude that maybe Tom is a cat from the saiyan's homeworld and shares their same properties, which could explain a lot in the series.
