I once had people believe with me that many people, pretty much everyone around us must definitely be police informers or plain-clothes police or intelligence officers plotting to neutralise us non-conformists, because we were a huge threat. I told them all the reasons they were and they believed it.
Truth be told, this took some uncommon circumstances, but not those would warrant such beliefs. The induced beliefs were so strong that some told other people in all earnest and with a gravitas that matched my own.
Disciples, spread the word!

Maybe needless to say, made my grandiose delusions skyrocket!
Not being in any way psychosis-prone just by anxiety, excitement or stress, after the episode they felt more alienated from themselves and embarrassed than I was. Which frankly, is great because now they know some of what I feel.
Luckily for them, they weren't as prone to depression. Pretty much blaming me for the ideas (I hate some people do that: really, I was insane, you are the sane one, if I can take responsibility, you certainly should! What do you think all this guilt is for I am now feeling: for me it is a story of a lifetime and you blame me!?)
My mother (same genetic load) and some friends may also at times believe pretty much anything as long as it is brought with some suppression of crazy. Especially when I wasn't yet diagnosed.