It seems kind of weird - why is there a random dinosaur hanging out in the lake? Upon closer inspection, you see that this is actually an ice cream stand and you're even more confused.
"Dinosaur Gertie's Ice Cream of Extinction" is an example of "California Crazy" architecture. This form of architecture became popular in the 1930's in California (which is why it fits so well into Disney's Hollywood Studios) and the purpose of this form of architecture was to attract attention. Buildings were often (but not always) made to look like what they sold inside:
Another example of "California Crazy" from Disney's Hollywood Studios would be "The Darkroom" on Hollywood Boulevard. This shop, shaped like a camera, is of course your stop for cameras and related photography items.
This goes well beyond a crazy form of architecture though - it is actually a tribute to Winsor McCay and his "Gertie the Dinosaur". In 1914, McCay debuted a unique performance combining vaudeville and a cartoon. Standing on a stage with a projection screen behind him, McCay would interact with his cartoon dinosaur, Gertie. He had his drawings timed out so when he asked the dinosaur to do things like lift its leg, it would. Taking this interaction to another level, he would even throw an apple to Gertie to eat (he achieved this by palming the apple in his hand during the toss). In a grand finale, McCay climbed on top of Gertie by walking off stage just as a cartoon version of himself appeared.
McCoy's live performance was later turned into a moving-picture to be shown in theaters. The film added a backstory to the performance and is about 12 minutes long, with about 5 minutes of the original animation. The only change in the original animation was replacing the apple with a pumpkin. Watch it here:
So the next time you're in Disney's Hollywood Studios, stop by and pay some respect to Gertie and Winsor McCoy for truly paving the way for future animators like Walt Disney.
Also, be on the lookout for Gertie's footprints from where she entered the water!