I watched S2 not that long ago and I still wouldn't have realized they were the same actor if the name hadn't nagged at me.
I've now seen Dean Stockwell in 2-3 episodes and he's magnificent. I love the reaction during the scene where he meets himself in the brig.
"I'M NOT A CYLON!!!!! Oh..."
I'm currently rewatching and just finished the two parter where they're searching for Starbuck. Some things are happening way earlier than I remember, like I didn't remember Hot Dog being introduced so early.
On my first viewing, (I watched the first two seasons before season three aired [I only decided to watch it because I wanted to see what Dwight Schrute was so obsessed with

]), I had never watched the original series. I thought the design for the Battlestars were a beefed up Runabout from DS9. Little did I know it was the opposite
Baltar is a scumbag and loathsome, but James Callis plays him in a way that makes him fun to watch (especially when Head Six puts him in uncomfortable situations) and I find myself laughing out loud very often when he's on screen.
Colonel Tigh is gruff and a mean bastard, kind of a space-Mr. Lahey, but he grew on me first time around in Season Four.
But, besides Starbuck and Baltar, I think the real standout of the show is Edward James Olmos as Commander Adama. His "We are at WAR" speech gave me chills, his glare could bore holes through whoever was on the receiving end. His bullshit "13th colony of Earth" speech at the end of the miniseries had me believing
My biggest complaint would have to be Caprica. They ended the show right when it was REALLY getting good
