Earl's picture
Earl Nigma was the brother of Alexander Nigma and the presumably the first janitor of A Nigma High.
History
Before the series
There is a painting of him in room 113B, which appears similar to a janitor's closet, further indicating that he was a janitor. His painting appears in The Theme Team and again (albeit quickly) in The Dance Part 1.
Gallery
His Nameplate
Earl and Alexander Nigma