Throughout the series, Martin is normally seen without a shirt, (not in a sexual way) but this is because he is apparently 'bloody boiling'.
In one episode, Adam's butt is visible but only for a few seconds, not sexualised.
Jonny keeps on giving Adam a wedgie, and later in the episode, the pyjamas bottoms rip, showing Adam's bum.
There is a scene in an episode where Jim where's a fake penis, and then another character plays with it
Val often wears low cut revealing shirts.
In season three, Johnny puts up dirty posters and pictures up on Adams wall. Adams girlfriend walks into his room and finds the posters. It shows girls in bikinis, girls bending over etc: It is shown! Quite graphic.
In most episodes there are a fair amount of sexual references, and in one episode there is a reference to molestation. The sex references are not strong, and are instead fairly moderate. Occasional references to sexual acts throughout the series.