Indiegala regularly has happy hours for their bundles.
However do not believe it is really cheaper or a happy hour in the traditional sense where for the normal price you get a 2 for 1.
While Indiegala's happy hour does give you extra copies if you buy the bundle as a gift, it also hikes the prices beforehand.
Here is an example using the Riddles Bundle:
Cheapest discounted price for the full bundle: $1.49 (for 48 hours at some time when the bundle is live)
Normal price for the full bundle: $2.99 (this is the price one would expect to be used for the happy hour)
Happy Hour price for the full bundle: $3.74
I think this is a dodgy business practice and is not "happy hour". It is essentially another offer where at a higher price you can get multiple copies of the bundle. Of course, the number of extra bundles you receive also depends in which week of the bundle's publication you buy it. The earlier in the publication cycle the more extra copies you get.
While the price of $3.74 is still great if you and a friend want the full bundle, I think the price should not be inflated for happy hour. Just trying to make people aware of it.