I am aware of idiom 'needle in a haystack' which means something hard to get. Is 'hippo in a haystack' opposite of it?
The expression hippo in a haystack does not appear on the Ngram corpus.
- The first use of hippo in a haystack on the internet seems to appear on September 22, 2013 in Seton Magazine's Hippo in a Haystack Color-In campaign:
... Why is the hippo in the haystack? Why is the chicken doing with the hammer?
- At around the same time, Dakota Riemersma won the MI Rock 2013 Junior Writer contest with a story entitled CRYSTAL FOREST, in which she used the expression:
We pulled into a clearing and there it was, Crystal Forest. First of all I only saw three trees and they stuck out like a hippo in a haystack.
This usage seems to approach the meaning of the idiom stick out like a sore thumb:
Fig. to be very obvious.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
- It appears in a comment by exelion on an article about missing Afghan Soldiers:
Three people that will appear of middle eastern descent to most Americans disappear in the middle of New England. First off, that's like finding a hippo in a haystack. In some parts they might be the only non-white for miles.
Again, this seems to be the exact opposite of the idiom finding a needle in a haystack:
An item that is very hard or impossible to locate,
- Currently, Jahanna Shilden has a database listed on Github.com:
Experimental in-memory data store designed for multi-node replication.
This moniker also seems to play on the idea that things will be easy to find in the database.
Although it has not reached the level of idiom, the expression plays very closely with two well established idioms. Since it employs imagery that is superior to stick out like a sore thumb, it is quite likely to catch on with a clear meaning:
clearly visible; obvious; easy to find.