What is Pikablu?
The veterans would know this... Pikablu was the alleged 154th Pokemon in the 1st generation. Rumours of it started to fly around the Internet after people saw Marill (In Pikachu's Vacation, the short snap before the 1st Pokemon Movie) and believed it was related to Pikachu.

Which versions were we "supposed" to get Pikablu?
The rumours started in the Red and Blue days, but it really built up when Yellow was released. It seemed that many people thought it was possible to obtain the Pokemon from Pika's Vacation in Yellow, including Togepi.

When was Pikablu proven to be fake?
There were two important parts to dispel the Pikablu myth. The first was pretty obvious; people tried out some of the alleged "cheats" to get Pikablu and got nothing out of them (or corrupted their data with fake Gameshark codes). There was a counter to this negative backlash, however; a few inventive players continuously re-posted their methods for obtaining Pikablu with different sets of variables, such as "Catch 150 Pokemon, beat the Elite 4 100 times, have a lvl 100 Magikarp etc". The real blow to the Pikablu phenomenon came when Marill was officially announced in Gold and Silver. Even though Marill was still rare, Nintendo stated in it's GS manuals that quote "No Gold or Silver Pokemon can be transported to the older versions". Opposite is a faked screenshot of a Pikablu sighting in RBY, courtesy of trsrockin.com.

How many ways were there of getting Pikablu?
Many, many MANY ways have been uploaded to the Internet, for all to see and be fooled. Usually the methods involve giving certain characters an item or placing a certain Pokemon at the top of your squad list, while a few Gameshark codes were placed on game sites, stating that Pikablu would be the first Pokemon you would encounter after entering the code.

What was the most common variable/part in all the methods of obtaining Pikablu?
Put simply, you must have finished the game in order for the methods to "work" (by finished, I mean you should have completed your Pokedex, beaten the Elite 4 and the Gym Leaders). Then you're supposed to follow a long-winded sequence of actions which would get you to Pikablu.

These methods all look the same... Any more?
Remember, it's been 5-6 years since Pikablu was officially blanked out from the speculative Pokemon public. With every year, the more questionable methods are being erased from Internet history, leaving only a few prominent ones behind.

For example, back when I was in Year 7, I thought it was possible to get Pikablu. One of the methods I tried was the following; Talk to the thirsty girl at the top of the Celedon Dept. Store 200 times, and she will say "Urghhh! I've had enough of you! take this POKEMON and leave me alone!"... Yes, it was a lame method, but I was young and fell for it...