Although not an episode, per se, Star Trek IV: The Voyage Home
will cheer me up every time. It is full of laughs, as well as action and drama.
Episodes which cheer me up: TOS: The Trouble with Tribbles
; DS9: Trials and Tribble-ations
and Little Green Men
“When all Americans are treated as equal, no matter who they are or whom they love, we are all more free.” -Pres. Obama
"A great democracy does not make it harder to vote than to buy an assault weapon." -Pres. Clinton