Ellen DeGeneres is famous for pranking her guests ... but this time guest star Dennis Quaid was in on the joke!

Ellen had Dennis mess with a nurse on set, who was trying to help him with an array of bizzare health problems.

Check out their hilarious scheme in the clip above!

From lung problems to shrinking, Quaid had the unassuming nurse go through a variety of ridiculous tests with the help of DeGeneres instructing him what to do next in his earpiece.

The poor nurse didn't even understand what was going on when Dennis made the big reveal.

Ah, Ellen we love you for always bringing the laughs.

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