What does "tack on to [something]" mean?

Native speaker’s answer
Rebecca
To "tack on something" is to add something extra. To join on to something. Here he's saying that the fact that he's a pickle should be enough to amaze Morty without any additional information or tricks. Ex: If I could tack on to this conversation, I'd say I agree with Henry. Ex: They tacked on an additional charge for food at the hotel.