Mr. Mole is one of the supporting antagonists of Thumbelina. He is an obese brown mole. He wears an Elizabethan-type-clothing, he is greedy, gluttonous, and materialistic, so he has a hatred to the sun, birds, and beetles because he obviously kills beetles, stuffs them and pins them to his wall, he lives in a house which is a crown underground with all of his gold, money, and jewelry.
Ms. Fieldmouse introduces Mr. Mole to Thumbelina and convinces him that she's from out of the ground and Ms. Fieldmouse and Thumbelina bought Mr. Mole some corn cakes to try, he digs in the basket with his hands and gobbles gluttonously and he talks about how he went up but it was too bright for him, forcing him back to his tunnels where they are "dark and decent". Ms. Fieldmouse and Mr. Mole want Thumbelina to tell and sing him a sad story. Mr. Mole tells a story about how he found a seemingly dead bird that got into his tunnel, Thumbelina and Ms. Fieldmouse were shocked and Thumbelina knew the bird named Jacquimo who got injured and is saved and healed by Thumbelina. Mr. Mole needed a word with Ms. Fieldmouse that he has a meeting to take a wife and Mr. Mole asked her to persuade Thumelina to marry him so she can keep him company and tell him stories. Ms. Fieldmouse is shocked but agrees and Mr. Mole offers her a gold coin as a reward. Ms. Fieldmouse suggests Thumbelina to marry Mr. Mole, but Thumbelina doesn't love him.
The Little Jitterbugs puts a fire above Frozen Prince to let the ice melt. They notice Mr. Mole's gonna marry Thumbelina, when the ice melts, they will tell Cornelius about it.
In the morning at Mr. Mole's Wedding, Thumbelina approaches sadly to the Mole but thinks of her true love, Fairy Prince Cornelius. But she gets distracted by a Reverend Rat, The priest who asks her that Thumbelina does take Mr. Mole to be her husband, but Thumbelina answers "Never!". She tells him that she cannot marry Mr. Mole and she doesn't love him. The crowd gasps in alarm, Grundel Toad crashes the roof down to the ground, Thumbelina kicks Grundel Toad's leg and runs away, Mr. Mole shouts "After Her!" and brings his guests as an angry mob to go after Thumbelina. The Beetle, Grundel's henchman, hops down to catch Thumbelina, but fails. Soon after, the mob chases Thumbelina across a stone bridge over a sheer drop hundreds of feet down, and Cornelius fights Grundel. After the toad falls, taking the prince with him, Mr. Mole and his mob continue to try to catch Thumbelina, but Thumbelina opens an exit and climbs out of the hole while the jewels and coins tumbles down towards to the Mole and his mobs and they were chased away by the avalanche of money.
In the end, Mr. Mole redeemed himself and so has Ms. Fieldmouse and they are seen again and got married during the end credits.
In some versions of the story of Thumbelina, he seem to have a friendly figure. He is often portrayed as at least somewhat more sympathetic than the Toad or the Beetle, though still an undesirable match for Thumbelina. They at least give him a happy ending of his own, with him ending up marrying someone else after Thumbelina leaves.
Despite being a supporting antagonist, Mr. Mole's desire to marry Thumbelina was the bigger threat and he turned out to be more dangerous than Grundel (although the latter also sought marriage).
His real age is unknown, but the actor providing his voice was around 54 years old at the time.