It's possible Crocker got Cosmo and Wanda back for a short time before losing them again as Timmy done the same dozens of times.
Fairies have bad memories, but Poof called Timmy by his name sometimes.
In this episode, Wanda says that fairies have bad memories and that is why they don't remember Sparky being with Crocker. However in The Secret Origin of Denzel Crocker!, it is revealed that the reason they don't remember ever being Crocker's godparents was because of Forgeticen and they remember Timmy's name just fine.
Is there a reason why Crocker didn't try to post the video footage of fairies?
When Cosmo and Wanda are trapped in the electrodes and Cosmo says, "A party? We should do the underpants dance!" Sparky should have become unhyptnotised then. It is not until "underpants" is mentioned again that Sparky becomes unhypnotised. This error makes the rest of the episode uneven. From here on out this error makes Sparky the opposite of what he should truly be (being hypnotized vs not being hypnotized).
Also, it's weird that Sparky haven't noticed that he had a microchip in his tail until now.
Mr. Crocker's record tape is different from Sparky's one.
In Sparky's tape, Jorgen took him, Cosmo and Wanda when he was in trance but in "Fairly OddPet", he is normal. It could be because Jorgen found out about the hidden microchip.
When Jorgen took away Cosmo and Wanda from Crocker, immediately he should have erased his memory, and that was what he made originally in The Secret Origin of Denzel Crocker!, and because Crocker in the present did not remember anything from the past.