The dime is hidden in Scrooge's "worry room." This was a room featured in a few episodes of the original series, designed with a circular rut in the floor so that Scrooge can pace nervously.
Webby's doll form resembles that of her appearance in the original series, along with her Quacky Patch doll from the Original DuckTales (1987), which also slightly references a scene from Night Terrors (2011), which featured David Tennant (Scrooge) and Catherine Tate (Magica).
The plot of Magica tricking someone into getting her past Scrooge's Booby Traps so she can reach his Number One Dime was also used in Dime Enough for Luck (1987) of the Original DuckTales (1987). In that episode she did so through Gladstone's luck, but in this episode she did so through Webby's trust to Lena.
The Unicorn that Webby faces off has a similar appearance to the one faced off by Mabel Pines in Gravity Falls (2012).
Tenderfeet holds a photo of Donald and his nephews making a similar pose to what was used in the promotional artwork for Quack Pack (1996).