Generally, you'd want to do it in the other order - cream ale followed by the IPA as you will get some hop transfer. If the IPA was not over the top in hop content/bitterness and you don't mind a bit extra hoppiness in the cream ale, go for it - you may love the results. Otherwise, best to wash before using.
Atomic Dog Brewery
On Deck: Centennial IPA, Dry Irish Stout
P: Cascade Pale Ale
T: Carbed Crystal Light, Root Beer, Vanilla Cream Soda, Tripel IPA, Apfelwein
e^(pi*i) + 1 = 0