Mom is a t-rex dinosaur in which the eggs were stolen during her absence. Furious and probably very worried, she does not hesitate to leave the world in which she lives to find her hatched children, and what a surprise to see that lazy sloth daring to stand up to her! Surprised, but not dazed, she rightfully takes her offspring with her, along with Sid back to her home in the underground dinosaur world.

Although initially terrifying, she is shown to have a heart towards her children and Sid, and will do anything to defend them from Rudy.