Near the end of the movie when Tip and Dash are going into Morgana's cave to help Melody(around chapter 16 on DVD) Undertow comes up behind them. He is really big so he covers the whole entrance to the cave. But when Dash jumps on Undertow, you can see that Undertow now isn't even that much bigger than Dash, when before Dash was the size of one of Undertow's tooth! I think it's a really big mistake, they should pay more attention.