Screenshot from Voltron, Defender of the Universe
Voltron is a shape-changing giant robot featured in the 1980s animated self-titled television series.
The television program would be followed by a successful series of toy vehicles that could be assembled. According to Matt, from X-Entertainment;
Liam's Voltron in Charlie's flashback in ("Fire + Water").
Getting the Voltron lion set was the kid equivalent of getting a brand new Ferrari. The implications and rise in your social status afterwards were nothing short of amazing. This was the toy to have. The thing that a lot of people don't remember or don't want to admit is that Voltron was never that big of a genre. I'm not saying it was small—it was huge and pretty damn popular—but in the years it was originally out there, there were several lines that were much larger. But this toy transcended any worries about how many of your friends watched the cartoon. It didn't make a difference if you even knew who Voltron was, much less the white-suited heroes who jumped into mechanical lions and flew threw tunnels. Why? Because it was huge, made of metal, and looked cool. That's all it really needed.
In Charlie's flashback-dream, ("Fire + Water") he remembered the Christmas when his brother Liam received a Voltron. Charlie could not find any present for himself, but his mother soon revealed that Father Christmas brought a piano for him. Due to the vast difference between the presents, Father Christmas would ensure that Liam would not feel left behind, by giving him the best of Christmas toys. As Voltron was on screens in 1984 and Charlie Pace was born in 1976 (according to the Drive Shaft website), that makes Charlie 8 when he got the piano if the "real" and storyline timelines are consistent.