It's gotta be season 5. Think about it. We've had:
- Cheese a Go-Go
- The Buck Swaps There
- Say It Isn't Sew
- Something Old, Something Bloo
- The Bloo Superdude and the Magic Potato of Power
- Schlock Star
- The Bride to Beat
- Affair Weather Friends
- Ticket to Rod
- Better Off Ed
- The Little Peas
That's 11 episodes, not counting "Nightmare on Wilson Way", which is the Halloween special and doesn't count for the season. (Like "A Lost Claus")
The seasons all have 13 episodes.
OK, if you want to get technical, you can argue that "House of Bloo's" & "Good Wilt Hunting" only count as one and the episodes with two 25-minute segments count as two.
So, in that case, it'd look like this:
Season 1: 11
Season 2: 15
Season 3: 13 (or 14 counting "A Lost Claus")
Season 4: 12
Season 5: 11 (So far; or 12 counting "Nightmare on Wilson Way")
But I digress. Every season has 13 30-minute episodes, whether they be longer or shorter. "A Lost Claus" & "Nightmare on Wilson Way" do not count.
So. 2 more episodes. Yes, I think "Let Your Hare Down" is season 5, then 1 more.