Cousin Mortimer is Basil's fiendish, sadistic cousin and The show's primary antagonist.
In the first series finale, he arrived and pretended to be kind and helpful to the local people but secretly he was stealing things and getting Basil into trouble. It's revealed that his full name is Mortimer Trouble Brush.
In the second series, he was released from prison and he was still causing havoc.
In the third series, he and Basil had to get along for 24 hours without fighting and arguing but it didn't seem to work. He also appeared at Basil's wedding when he was marrying evil Kelly Foxwell but in the end, Kelly liked Mortimer more than Basil. He returns in the Christmas special. He appeared in the fourth series in prison when he did something wrong that was unknown.
In the 2005 and 2006 Christmas specials.
His catchphrase is "Bang! Bang!", followed by the sound of two projectile ricochets.
- 5x02 Fox Rocks
- 5x04 Brush To The Future (animated segments only)
- 5x05 Kiss And Tell
- 5x07 Back to School (animated segments only)
- 5x09 Dave's First Girl Friend (animated segments only)
- 5x10 The Sweet Smell of Success
- 5x12 Basil's Extravaganza
- 5x13 There's No Business Like Snow Business
- 6x01 Ballroom Basil
- 6x02 Basil's Angels 2 Fox on the Run
- 6x03 This Charming Man
- 6x07 Da Basil Code
- 6x09 Windbreaker
- 6x10 Dave's Apprentice
- 6x12 Basil Hood
- 6x13 Basil's Christmas Dinners
- He is voiced by Don Austen who also voiced Bingo Brush.
- He was the first fox to be introduced.