I wonder how often Si is confused with Fi. More than people think. Si is about impressions, perceptions, reflecting on the past and applying it to the present and future, personal sentimentality...Si users could actually be extremely introspective and self-aware. Si notices internal changes and differences in reactions to feelings, right? I think SJ introverts especially would be prone to reflection, because that's what introverted functions do, and the psychic energy flows inward. ISFJs could be very skilled in the intrapersonal intelligence.
And then Fe...some sensitive ISFJs might be very attracted to the "kind, gentle" stereotype that is associated with INFPs. Fe wants to affect the world and make a difference, to leave an impact. That desire could lead to idealism, which is also an INFP stereotype. And I think it's safe to say that almost all of SJs - or at least the vast majority - have some connection to 1. Whether a core 1, a 2w1, a 9w1, or one of those as a fix. (Really, an ISFJ with absolutely no connection to 1 seems exceedingly rare.) 1 is all about rightness and how things ought to be, right? 1 is moral and principled, in tune with what is right and what is not. This could easily be mistaken for the INFP "core values" and "personal sense of what is right." Fe also knows what is right; morality is not exclusively Fi. Maybe Fe is just more prone to overarching, all-applicable rightness? Like, a strong morality that applies to humanity. That's just speculation though.
Ti...I know much less about this function in general. But I think Ti enjoys playing with logic. It develops internal systems of how things work and fit together, correct? This adds an intellectual side to the ISFJ. Their tertiary Ti is offended by the "stupid homebody" stereotype, so they would naturally claim another type. The ISFJ is perfectly capable of deep conversations - Si reflects on what used to be, Fe has insight into relationships and maybe humanity, and Ti has systems and internal logic. Imagine the philosophical conversations that could arise from that! Ne could also come into play by drawing parallels, metaphors, and connections - and might add a touch of quirkiness and idiosyncrasy that is always associated with NPs.
Si notices what is different, in the self and in others. This could provide profound insight into the nature of human beings and the fluidity of reality. And imagination isn't really a type thing - anyone can be funny.
A strong romantic streak could also stem from Si. "Remember the days of old, when all was rosy?" "I wish I could be carefree like a child again." "I want to read through all my old diaries and hold on to memorabilia so I can reflect." "I love thinking about who I used to be, and who I am now because of that." It could be hard for an ISFJ to hold on to reality, because they're prone to getting lost in past reflections and thoughts. Add that to their introversion and need to withdraw. This could totally lead to a dreamy disposition, like an INFP.
I know some of this is just weaving in what others have suggested here, but a great deal of it is my own thinking. What do you think?
I don't mean to pry, but why would you even make the eyes?
I need some Si/Te groundedness at the moment, so I'm gonna hang out here for a bit
ENFP: We put the Fi in Fire
Motivation: Dark Worker
Alignment: Chaotic Neutral
MTG Color: black/red
Male Archtype: King/Lover
"You are a gay version of Gambit" Speed Gavroche
"I wish that I could be affected by any hate, but I can't, cuz I just get affected by the bank" Chamillionaire