These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Amazingly, every episode of the series so far has had a song sung by a different member of the gang. But the best one by far is Nelson's song "Breaking Up Is Such A Faff" in Episode 6.
Not quite every episode. In episode 5, Nelson tries to sing to Destiny about his love for her, but she ends up being dragged away by Gary shortly after the song begins. However, to make up for this, he sings lead on two songs across the whole series instead of one like everyone else.
To make Vince's incident of eating children even worse, they were his OWN offspring!
The first time, the second time it was Nelson and Kali's, she was disappointed that her attempt to create a master race of super predators resulted in an ordinary pigeon with red feathers so she had Vince dispose of it.
And now, there is a whole song dedicated to Vince's complete monsterness. And it isCatchy as hell.
Crossing the Line Twice: Like many UK sitcoms Mongrels is dedicated to offending as many people as possible solely in the name of a good hearty laugh.
Family Unfriendly Aesop: Nelson dates a chicken in the first episode, which is treated like an interracial relationship... but then the chicken turns out to be evil.
The circle stroking mentioned above, and one of Marion's attempts to break up Nelson and his sister (Nelson's sister, not Marion's) involved dressing in drag and claiming to be his wife.
Nelson And Vince get a lot of Ho Yay when they are stuck in the "Island" and actually end up having sex.
Les Yay: Episode 3 involves Kali and a lesbian crow.