The Sexaholics of Truthteller Planet

by Foggy Brume
Answer: JUST DO IT

All aliens are referred to by their initials. X# refers to the statement alien X made on that numbered Day.

Day 1
D1 must be false (a Gnytte cannot claim to be a Mnaivv), so D is a Mnaivv. For the statement to be false then, J is a Gnytte, and J1 is true.

Of A, G, and N, only one is a Gnytte. G1 and N1 are opposites; one is a true statement, the other false. This accounts for our Gnytte, so A is a Mnaivv, and A1 is false.

If C1 is true, then F is a Gnytte (since A has been to be a Mnaivv). If C1 is false, then F is a Mnaivv. Either way, C and F are the same type, and B is a Mnaivv. This makes K1 false, thus K is a Mnaivv. We have now accounted for 5 Mnaivvs (A, B, D, K, and either G or N), so F1 is true, making F a Gnytte, and from above, C is a Gnytte as well.

E is infected. If E is a Mnaivv, then both H1 and I1 are true. If E is a Gnytte, then H1 and I1 are false. Either way, H and I are the same, making L1 false, and L a Mnaivv. O1 is false, therefore O is a Mnaivv as well.

We have now accounted for eight Mnaivvs (A, B, D, L, K, O, 1 of G/N, and at least 1 of E/H/I). This makes M1 false, therefore M1 is a Mnaivv. G1 is false and N1 is true. G is a Mnaivv, so E1 is true, which makes H1 and I1 false. On Day 1, our aliens look like this:

ABCDEFGHIJKLMNO
FFTFTTFFFTFFFTF
Infected: E

Day 2
J did not have sex, and therefore is still a Gnytte. A therefore had sex with D. Suppose A is still a Mnaivv. It would mean that neither A nor D is infected (otherwise both would be Gnyttes). This would make A2 true, however, which is a contradiction. A (and D) are now Gnyttes, and A2 is true. Since D is therefore not infected, but at least one of the two is, A is infected.

N and M had sex. Regardless of infection, M must still be a Mnaivv. Therefore M2 is false, and N is infected, making N a Mnaivv, and N2 false.

E did not have sex with J (solo), N (had sex with M), C or F (N2 is false). This accounts for all of our Gnyttes. E's partner was therefore a Mnaivv, and since E is infected, E is now a Mnaivv and E2 false. B's partner last night was a Gnytte. Regardless of infection, B must still be a Mnaivv. By the same logic, O is also a Mnaivv, and again by the same logic, I is a Mnaivv. B, O, and I all had sex with Gnyttes. Since I2 is false, I and F had sex.

Of the five Gnyttes, one had sex with M, one didn't have sex, and the other three had sex with B, O, and I. H2 must therefore be false, while K2 must therefore be true. H had sex with a Mnaivv the previous night, and is still a Mnaivv, so H is not infected. By similar logic, K or K's partner is infected.

C & E had sex with B & O in some order. For G2 to be true, either C&B had sex, or O&E had sex, but not both. If C&B had sex, only O&E have not been paired up, so they had sex, which contradicts G2. The same is true if O&E had sex. Therefore, G2 is false. G is therefore still a Mnaivv, and could not have been K's sex partner. G and H had sex, and so did K and L, making L2 true. C is therefore infected. Since C had sex with a Mnaivv, C is now a Mnaivv as well. We have five Gnyttes today, and since D2 is true, C and O had sex, leaving B and E. (C2's statement is false, but it does not help us.)

ABCDEFGHIJKLMNO Who had sex
FFTFTTFFFTFFFTF A&D, B&E, C&O, F&I, G&H, K&L, M&N, J
TFFTFFFFFTTTFFF 
Infected: ACEN, either K and/or L, either F and/or I

Day 3
H is still a Mnaivv, so H3 is false. Since either I or O is infected, I and O are now both Mnaivvs.

Since O3 is true, L and E had sex. E is infected, making E and L both Mnaivvs today. L3 is false, so I had sex with someone who is uninfected, which would be O. Since either I and O are infected, and O is uninfected, I must be infected. I3 is true, so C, previously a Mnaivv, had sex with a Mnaivv. Since C is infected, C is now a Gnytte. Since C3 is true, J and K had sex. Regardless of infection, they are both still Gnyttes today.

Suppose D3 is not true. For D3 to be false, D would have to be a Mnaivv now, which would require having sex with a Mnaivv, which would make D3 true, a contradiction. D3 is therefore true. Since D, as a Gnytte, had sex with a Mnaivv, neither was infected. A, as an infected Gnytte, did not have sex with D, J, K, or L, the only other Gnyttes. Therefore, A had sex with a Mnaivv, and is now a Mnaivv as well. A did not have sex with N. N did not have sex with J, K, or L (already claimed). Since N is infected, N did not have sex with D either. N's partner was a Mnaivv, making N a Gnytte today.

N3 is true, so B is still a Mnaivv. B3 is false, so last night B had sex with an infected individual. Since B is still a Mnaivv, this partner must have been a Gnytte. This cannot be D (D is not infected), so it's A. K3 is true, so M is a Mnaivv as well. M either had sex with D or an uninfected F or G. If it were one of the latter, this would give us only seven Gnyttes (D's partner would remain a Mnaivv; M and M's partner would remain Mnaivvs). This contradicts J3, so M had sex with D (M is also uninfected). Since there are more than seven Gnyttes, either F or G must be Gnyttes. It's impossible for just one to be a Gnytte, so both are. F3 is true. Of the three people left, F could only have sex with G, and since F and G changed to Gnyttes, F must be infected. This leaves C to have sex with N.

ABCDEFGHIJKLMNO Who Had Sex
FFTFTTFFFTFFFTF A&D, B&E, C&O, F&I, G&H, K&L, M&N, J
TFFTFFFFFTTTFFF A&B, C&N, D&M, E&L, F&G, I&O, J&K, H
FFTTFTTFTTTFFTT
Infected: ACEFIN and K and/or L
Uninfected: DGHMO
Unknown: BJ

Day 4
D and J, regardless of infection, are still Gnyttes. D4 is therefore true. B, H and M have been Mnaivvs only for the first three days. M has had sex with D and N, but they could not have had sex. H has not sex both nights, so the person referred to in D4 is B. B's partners were A and E; they therefore had sex. A and E must now be Gnyttes. E4 is true, so O did not have sex last night. O must still be a Gnytte. O4 can only refer to G and K, so they had sex. Since both were Gnyttes, then they are both still Gnyttes today, regardless of infection. This gives us all seven Gnyttes per clue A4. Everyone else must be a Mnaivv today. The four people who were Gnyttes yesterday must have had sex with Mnaivvs, giving us four Gnytte-Mnaivv pairings where at least one individual was infected.

C4, M4 and N4 are all false. C had sex with a Mnaivv, but C4 rules out B, H and M, leaving only L. M had sex with a Gnytte, but M4 rules out F and N, so M had sex with I. N had sex with a Mnaivv, but N4 rules out B, so N had sex with H, and F had sex with B. F4 is false, so B is not infected. K4 is true, so J cannot be infected (J was left out on Night 1). This leaves just K and L, and since G4 is true, both must infected for there to be 8 infected individuals.

ABCDEFGHIJKLMNO Who Had Sex
FFTFTTFFFTFFFTF A&D, B&E, C&O, F&I, G&H, K&L, M&N, J
TFFTFFFFFTTTFFF A&B, C&N, D&M, E&L, F&G, I&O, J&K, H
FFTTFTTFTTTFFTT A&E, B&F, C&L, D&J, G&K, H&N, I&M, O
TFFTTFTFFTTFFFT
Infected: ACEFIKLN
Uninfected: BDGHJMO

Day 5
A5 cannot be true (if A had sex with a Mnaivv, then as an infected Gnytte, A would be a Mnaivv today). A could not have gone solo the previous night, since A has changed mutation. A had sex with a Mnaivv, and F is the person referred to in the clue. (D had sex with A on Night 1, A had sex with B on Night 2, B had sex with F on Night 3.) A and F had sex, so F is still a Mnaivv. F5 is false, so C did have sex with the person referred to in clue F5. (C had sex with L on Night 3, L had sex with E on Night 2, and E had sex with B on night 1.) So C and B had sex, making both Gnyttes today.

B5 is true, so D had sex with the person referred in that clue. (A had sex with B on night 2, who had sex with F on Night 3, and F had sex with I on Night 1.) D and I had sex, making both Mnaivvs now.

C5 is true, so H had sex with the person referred to in that clue. (M had sex on Night 1 with N, who had sex with C on Night 2, who had sex with L on Night 3). This makes H and L both Gnyttes.

This leaves EGJKMNO. D5 is false, so J is a Mnaivv, and had sex with an infected Mnaivv, which can only be N. N5 is false, so K had sex with an infected individual, who can only be E. J5 is false, so G did have sex with someone. O did not sit out, since O sat out previously. M sat out, and G and O had sex.

ABCDEFGHIJKLMNO Who Had Sex
FFTFTTFFFTFFFTF A&D, B&E, C&O, F&I, G&H, K&L, M&N, J
TFFTFFFFFTTTFFF A&B, C&N, D&M, E&L, F&G, I&O, J&K, H
FFTTFTTFTTTFFTT A&E, B&F, C&L, D&J, G&K, H&N, I&M, O
TFFTTFTFFTTFFFT A&F, B&C, D&I, E&K, G&O, H&L, J&N, M
FTTFTFTTFFTTFFT
Infected: ACEFIKLN
Uninfected: BDGHJMO

Take the infected individuals, and their status each day. Treat as binary to get the answer JUST DO IT.