Meg: Meggymoo, Babygirl, Babby & Flash (due to her being so alert, well, quite the opposite TBH!)
Jakey: Jakeyboy, Jakeymondo, Babyboy & 'My big, bad, boy'!
Lennie: Gnasher - simply because he looks like him, because he's small, a rascal & has mad black wirey hair....he Gnashes too!
Gnashy, Gnash Gnash, Gnashy boy & various other variations on the Gnash theme, 'my little man' & 'Commissioner' - I call him that a lot & he's had this nickname ever since that ITV Flood drama a couple of years ago, where the person in charge of London's flood defences was called Commissioner Nash!