In Act 5, scene 5, a bunch of kids take part in the prank played on Falstaff: they dress up like fairies, head to the woods, and attack Falstaff by burning him with candles and pinching him with their grubby little fingers. Of course, Falstaff is convinced that he's being attacked by real hobgoblins.
If you think all this sounds like your local children's theater group or that crazy little Halloween pageant you were in when you were nine years old, you're on the right track. The Children of Windsor wear costumes and masks, they sing and dance, and even have to rehearse their parts with Master Ford (4.5.63-64).
To us, this is an obvious shout-out to child actors. And child actors were a Very Big Deal in Shakespeare's England. Children's theater groups offered up some seriously stiff competition for adult acting companies (like Shakespeare's).
Speaking of children: what is up with the two kids who almost marry Caius and Slender? During the prank in the woods, Caius and Slender each think they're running off to elope with Anne Page when, in fact, they run off with two boys dressed in fairy costumes (5.5). Slender is so embarrassed about mistaking a "boy for a girl" (5.5.176) that he assures everyone (twice) that he would never have had sex with him (5.5.172, 5.5.177). We're sure you can come up with plenty of things to say about this but here's our best guess:
In Shakespeare's day, women weren't allowed to be professional actors so, female roles were often played by boy actors with high-pitched voices and pretty, youthful features. At the end of Merry Wives, Shakespeare draws our attention to the fact that when any heterosexual couples get married or hook up in one of his plays, audiences are actually watching two male actors get together on stage. Shakespeare loves to do this. Go read the end of Twelfth Nightif you don't believe us.