Daniel is wrongly diagnosed with schizophrenia after being infected by an alien organism that causes him to suffer disturbing hallucinations and increased paranoia.
"Legacy" provides examples of the following tropes:
- Arbitrary Skepticism: Dr. Mackenzie seems to write off Daniel's ramblings about Ma'chello and alien devices as the delusions of a crazy person - which would be perfectly understandable for any other psychiatrist, but given that Mackenzie works for SGC and knows the kind of things that tend to go on there, you'd think he might at least give it the benefit of the doubt.
- Although to his (and the writer's) credit he obviously can tell Daniel is more lucid and decides to check on what he says. When it turns out to be true he immediately sends him back to the SGC.
- Bedlam House: The mental hospital that Daniel gets sent to is very much the stereotypical Hollywood "padded cells and straitjackets" variant.
- The Cassandra: No-one really believes Daniel's claims that he isn't crazy until Teal'c gets sick.
- Contamination Situation: The organisms manage to breach the containment chamber and infect O'Neill, Carter and Fraiser, causing Hammond to seal them in the lab in an attempt to contain the situation.
- Continuity Nod: The Reetou are briefly mentioned as a possible explanation for the deaths of the Goa'uld.
- The manner in which the organisms are transferred are with a booby trapped Gou'uld reading tablet, first shown in "Brief Candle".
- Cruel and Unusual Death: The hosts of the Linvris Goa'uld were left to slowly die of starvation in a sealed room after Ma'chello's organisms killed their symbiotes.
- Did Not Think This Through: Ma'chello.
- Created organisms to kill Goa'uld without killing their host, and to his credit they do that pretty well. However, he doesn't seem to have considered the possibility of the organism finding their way into someone who simply doesn't have a symbiote inside them, as the organism apparently just keeps trying to kill the symbiote that isn't there while driving the person crazy. Considering vastly more people won't have a symbiote inside them than those that will, that seems a drastic oversight.
- He also doesn't seem to have considered that the person his organism infects might have been freed from their symbiote by other means, given that they take Carter's protein marker as "job done." To be fair, given that Goa'uld would generally save themselves at the expense of their host, someone in Carter's situation must be a rarity to say the least, even unimaginable if you don't know the Tok'Ra exist.
- "Eureka!" Moment: Daniel gets one when he hears Machello's voice in his head after the organism leaves him, triggering a flashback to "Holiday" that helps him realize his symptoms must have been caused by one of Ma'chello's anti-Goa'uld inventions.
- Foreshadowing: Likely an unintentional case, but interesting nonetheless; after his first few hallucinations of the dead Goa'uld, Daniel speculates that they somehow cheated death by transforming into energy to hide from the system lords. Obviously that isn't the case in this episode, but it would later be revealed as pretty much exactly what Anubis did.
- Forgotten Phlebotinum: The Area 51 inventory files seem to show they've got a good dozen of Ma'chello's boobytrapped page turning devices; said devices contain technology able to remove a Goa'uld from a human without killing the host, something extremely useful to the SGC and which is otherwise only possessed by distant allies who often are unable to be contacted. And yet said tech is never brought up ever again.
- Go Among Mad People: Daniel starts acting a good deal less lucid and more noticeably "crazy" after getting sent to the asylum.
- Hallucinations: The main symptom caused by the organisms: Daniel sees the dead Goa'uld several times, in addition to wormholes in his closet and a symbiote going into O'Neill. When O'Neill and Fraiser are infected they begin to experience similar symptoms, mostly involving Carter as Goa'uld.
- Hearing Voices: Daniel hears creepy disembodied voices calling his name on a number of occasions. Everyone who is infected also hears Ma'chello's voice in their heads as the organism leaves them.
- Hollywood Psych: Doctor Mackenzie says early on Daniel is displaying signs of hebephrenic schizophrenia. This is an odd diagnosis, as the most prominent symptoms of this type of schizophrenia are disorganized speech, thought and behavior (for example, speaking in word salad or inappropriate emotional states for no apparent reason), which Daniel is not exhibiting so far. There are several diagnoses that would be more appropriate for his prevalence of hallucinations, including paranoid schizophrenia.
- I See Dead People: Most of Daniel's hallucinations involve seeing the dead Goa'uld in various places.
- The Immune: Carter is unaffected by the organism due to a protein marker left in her blood when Jolinar died inside her. With some help from an increasingly delirious Fraiser, she is able to use this to synthesize a cure for the others.
- Preemptive Apology: O'Neill when he realizes he's been infected:O'Neill: I'd just like to apologize in advance for anything I say or do that might be construed as offensive as I slowly go nuts!!!Fraiser: Likewise, Colonel.
- Not Helping Your Case: Daniel ends up lampshading this when he realizes that he's pretty much acting exactly how one might expect a crazy person to act.Daniel: Why is everyone so quick to assume that I'm crazy? That I'm dangerous, I'm out of control?![Very long Beat in which Mackenzie gives him a pointed look.]Daniel: ...I guess it's because I'm kinda acting that way, huh?
- Sequel Episode: To "Holiday".
- Side Effects Include...: O'Neill's comments regarding the doctors' theory that Daniel's "schizophrenia" may be the result of gate travel invoke this.O'Neill: Why can't we just put a little sign at the end of the ramp? "Warning: gate travel might be hazardous to your health." I could live with that.
- Smart People Play Chess: Daniel and O'Neill play a game of chess while Daniel is being kept in isolation on the base. The "smart people" in this instance applies to both of them since it's repeatedly shown throughout the series that O'Neill is a regular player.
- Unwanted Assistance: After the organism leaves him Daniel comes to the realization that the drugs intended to make him "better" are only clouding his judgement and making him appear more unstable than he is.
