The phrase
"old switcheroo" means to unexpectedly replace or exchange one thing with another, usually for a playful or deceptive purpose.
Full definition
Aw...
the old switcheroo!
Heloise gives Beezy's and Cerbee's brains
the old switcheroo after they crash the picnic she's been planning for Jimmy.
The last major title of note is Hulk, perhaps the year's most controversial release due to the studio playing
the old switcheroo with Mychael Danna's score and engaging Danny Elfman for a quick refit.
See if he can use his eyes, nose and thinking skills to find the treat after
the old switcheroo.
The Old Switcheroo: After your new cat has gotten used to her space, let her have some time out in the house and confine your other pets.