Jeff Heaney is a twat. He is also a supporting yet recurring character in the television series Peep Show, and is portrayed by Neil Fitzmaurice.
Jeff is a work colleague of Mark's at JLB Credit and an intimidating, manly bully from Merseyside. The two repeatedly clash, not least for the attentions of Sophie, who chooses Jeff but leaves him after he continues to chase women.
In the later series, as Mark and Sophie's relationship takes its course, he is frequently seen mocking Mark. After their relationship falls apart, Jeff appears to gradually get close to Sophie again. Mark's anger over this peaks when Sophie even considers naming their child 'Geoff'. However, Sophie sees no connection between this name and that of Mark's rival, instead claiming that she takes it from a relative. In series 7 he becomes the baby's godfather when Mark and Jeremy both fail to turn up on time, and it appears that Jeff and Sophie are back in a relationship by the end of the series, which is a major torment to Mark, who constantly believes that his son will think Jeff is his father. Jeff confirms they are back together when he comes to Mark's house to collect the baby in Series 8.