1. Donald Faison (Turk) as a Patient: In Season 6, Turk appears as a patient with a rare condition that forces him to wear a ridiculous mask. This was a meta-joke on Faison's part, playing with the idea of him being a celebrity appearing as a regular character.
2. John C. McGinley (Perry Cox) as a Patient: In Season 9, McGinley appears as an older, slightly senile patient with a bizarre obsession with the number 7. This self-deprecating humor, playing on the fact that he was the oldest main cast member, was a fun twist.
3. Neil Patrick Harris (Dr. Doogie Howser, M.D.) as Dr. Aaron "The Hammer" Harris: This appearance was a fun nod to Harris's earlier role as a young doctor in the show "Doogie Howser." His character in Scrubs was a skilled surgeon with a bad temper.
4. Michael Cera as a Patient: Cera, known for his quirky comedic roles, appeared as a hypochondriac who constantly believes he's sick with something new. His portrayal added a fresh comedic energy to the episode.
5. Bill Lawrence (Show Creator) as a Patient: Lawrence made a brief cameo appearance as a patient, proving that even the creator of the show wasn't above making fun of himself.
6. Eliza Dushku (Buffy the Vampire Slayer) as a Patient: While Dushku was already known for her role in "Buffy," this appearance provided a comedic contrast to her action-hero persona.
7. Sarah Chalke (Elliot Reid) as a Patient: Chalke played a different character, a woman who was the victim of a car accident and had to be treated by the Sacred Heart staff. This meta-joke played on the fact that Chalke was already a main cast member and offered a fun twist.
8. Heather Graham (Boogie Nights) as a Patient: Graham, known for her dramatic roles, appeared as a patient who was completely delusional and made the doctors think they were in a dream sequence.
9. John Ritter (Three's Company) as a Patient: Sadly, this was one of Ritter's last acting roles before his passing. He appeared as a patient with a heart condition, and his performance was both funny and touching.
10. Ken Jenkins (Dr. Bob Kelso) as a Patient: This appearance, while unexpected, made sense given the show's tendency to blur the lines between reality and fantasy. Kelso, usually in a position of authority, was humbled as a vulnerable patient.
11. Mandy Moore (A Walk to Remember) as a Patient: This appearance was a fun callback to Moore's early musical career. She appeared as a patient with a unique condition that caused her to sing at inappropriate times.
These are just a few of the many memorable guest appearances on Scrubs. What makes them surprising is the range of actors, their unexpected roles, and the humor derived from playing with audience expectations.