What is the talking centipede joke?

A man enters a pet store and speaks to the proprietor. “OK, I want to get a pet, but not a boring or typical pet – no cats, dogs, or birds – I want something unique.” The owner of the pet business informs him that he has a talking centipede. “Really?” asked the man, “and how much?” The owner informs him that the talking centipede is $50. The man accepts an unexpected offer, pays the money, and takes his new pet home.
On getting home he lays the matchbox with the centipede in it on the table, opens it, and says “Hello Mr. Centipede, Fancy going to the pub for a few drinks?” The centipede says nothing. Figuring it must be tired from the journey, he decides to leave it for an hour and try again later.
An hour later he opens the matchbox and says “Hello mr centipede, fancy going to the pub for a few drinks?” The centipede again says nothing. Starting to get suspicious the man decides he will give it one more hour, and if the centipede doesn’t talk, he will take it back to the shop for a refund.
An hour later the man opens the matchbox and says “Hello mr centipede, fancy going to the pub for a few drinks!?”
The centipede says “I heard you the first time!!! I’m putting my shoes on!”