Mother & Child Reunion, Parts 1 & 2!
Honourable mention to Holiday, Parts 1 & 2 (the "Joey & Caitlin get back together episode" for me, the "Craig, Manny, Ashley love triangle" episode to most of you!

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As for ones that deal with TNG characters ... the two parter where Emma finds her birth father, Shane, committed in an institution in Stoufville!
The episodes that I have never seen but want to are the ones where Snake and Spike get married!