I've noticed a lot of patterns in what types get mistyped, and how some MBTI-enneagram combos can make people get massively mistyped.
A lot of this is rambling and mental vomit, keep in mind.
1: I__P 1's often can appear to be like I__Js, and may mistype themselves that way. INTP 1s are sometimes mistaken for ISTJ or INTJ. E__J 1's may mistake themselves for introverts, especially the 1w9s. 1w2 T types mistake themselves for F types, they can often appear to have the F "warmth" but still use Te or Ti as a main judgment function. Same for 1w9 feelers, but vice versa. Can come off as T's, but still have Fe or Fi as a dominant judgment function.
2: 2's honestly seem to be universally F types, especially __FJ. Sometimes E_FP, but rarely I_FP. I_FJ 2's can mistake themselves for E_FJs, especially if they aren't a social last. In fact, social last 2's are really really weird to think about, I don't think I've ever seen one or met one... hmm. Should check my enneagram videos. I need to get around to posting that on here.
3: Can be literally any jungian type, but I don't really go around seeing introverted 3's very much. Type 3 seems to be almost dominated by S types, so for 3 I have ESXX/ISTP>ENXX> the others. 3's I notice are mostly these MBTI types- ESFJ, ESTJ, ESFP, ENFP, ISTP, ENFJ, ENTJ, ENTP, and ESTP. So basically every extrovert, plus ISTP for some reason. Think Shaq for ISTP 3, they are the sports stars and master athletes that are really practical and intelligent but also people friendly. Introverted 3's may confuse themselves for extroverts. I honestly don't see very many mistypings with 3's, except ENFP 3's seem to commonly think that they are ESFPs; or are just confused over the S/N dichotomy.
4: Mostly introverts. INTJ 4's often mistake themselves for INFPs or ISFPs. ENFP 4w5's mistake themselves for INFPs, INFP 4w3s may mistake themselves for ENFPs, ENFJs, or ISFPs. 4w3 introverts in general seem to be very stereotypically "extroverted," since type 3's are one of the three aggressive types. 4w5s seem to be stereotypically "introverted," with 4 and 5 both being withdrawn types. So yeah, easy to mistake yourself for another MBTI type if you have a hard time with the functions. A WORD OF CAUTION: 4 =/= FI!!!!!
ENTP 4's, though rare, are extremely, EXTREMELY inwardly conflicted. With having the 4's main motivations plus having Fi as their very worst function, they can be very very inwardly conflicted.
5: Seem to be almost exclusively introverts, INXX and ISTX, rarely ISFJ. I've never seen an ISFP 5. Also ENTP rarely. Most people who are 5's think that they are INTPs, hell a lot of 5's ARE INTPs. INFP 5's usually think that they are INTP or INTJ. ISTJ 5's may be confused on the S and N dichotomy, or may appear borderline on S/N. ISTPs seem to be 5w6s, hardly ever 5w4. The ISTs are more commonly 5w6, the INs are more commonly 5w4s.
6: 6's seem to be the classic ambiverts. They may be confused over E/I and T/F. The S/N and P/J dichotomies seem to be obvious in 6's, but not so much the other ones. You can see the mistypings possible there, I don't have to type it out.
7: Seem to be all extroverts and IS_Ps. Rarely ES_Js; ES_J 7's may have stronger "Ne" in MBTI terms. ES_P 7's usually mistaken for EN_Ps; since in most descriptions Ne dominants sound a lot like 7's. But they aren't capturing what Ne actually is in those unfortunately; most EN_P descriptions are just of 7's who have an EN_P preference and not just of EN_Ps. IS_P 7's usually mistake themselves for extroverts. 7w8 feelers can appear somewhat T like, 7w6 thinkers can be somewhat feely.
8: Most 8's confuse themselves for E_TJs. I've seen E_T_s, E_FPs, ISTPs, and INTJs as 8's. Most INTJ 8's are 8w9s. 8w9s can sometimes think that they aren't 8's because they are the "nicer" 8's, and most 8 descriptions are of 8w7s. E_FP 8's usually think that they are/are mistaken for E_TJs, ESFPs thinking they are ESTJs, ENFPs thinking they are ENTJs. ESFP 8's can also be mistaken for ESTPs. ISTP 8's are usually social last variant wise.
9: Most 9's tend to mistype themselves or question themselves in the enneagram/MBTI; since by definition 9's don't know themselves that well, or have a hard time doing that. We just know other people, and are detached from ourselves to be attached to the world. The stereotypical I_FPs are 4's, and I_FP 9's can seem to be I_TP from the untrained eye.
More to come as I think of it...