In the beginning of the episode, Dexter:
1: Wakes up with a grin on his face.
2: Dances while taking a shower.
3: Waits for the bus in a good mood with the sun shining.
and 4: Is greeted by all the teachers when he greets them.
After his lab is shutdown because Mandark threatens it, Dexter:
1: Is depressed while taking a shower.
2: Is gloomy when waiting for the bus in the rain.
and 3: Is ignored when greeting the teachers and then is trampled by peers and teachers when Mandark shows up.