The Pants-A-Phone are pants that have a sort of phone in them. It just appears in the episode: Spy Buddies. It is on Patricks's Bermuda-Shorts. You need to through in twenty-five cents with you want to call someone again. It is a running gag, because Mr. Krabs gave the pants to SpongeBob and Patrick, because he is known as a penny pincher.
Patrick: Self-destruct! (pushes button and the car explodes. Both laugh and shake off the dust. Patrick's pants phone is ringing) There's a call coming through on my Pants-A-Phone.
Mr. Krabs: (from the Pants-A-Phone) Krabs to Agent SpongeBob. Come in SpongeBob.
Patrick: It's for you.
SpongeBob: Agent SpongeBob here.
Mr. Krabs: You found out what Plankton's up to?
SpongeBob: I'm afraid we've lost him, Mr. Krabs.
Mr. Krabs: Well, find him, lad. I'm not paying you to goof off with Patrick.
SpongeBob: You're not paying me at all, Mr. Krabs.
Mr. Krabs: Exactly. So get to work. (hangs up)
Recording: If you'd like to make a call, please deposit twenty-five cents. (SpongeBob gets out a quarter)