Shazaam is an (apparently) non-existent movie starring Sinbad. The movie is described as portraying Sinbad as a genie.
While this Mandela Effect seems to be widely experienced, the movie has no evidence of ever existing. A description of the plot of the movie was posted on reddit by user /u/EpicJourneyMan:
"The movie came out on video (not sure it ever was released in the theater) in 1994-5, months before the release of "Houseguest"
The story revolved around a pre-teen/teen age boy and his 5 year old or so little sister who are living with their Dad (apparently the mother had died).
At some point, a lamp is put on the mantle of the fireplace and the boy rubs the lamp and Wham! a genie (Sinbad) appears.
The kids are freaked out and this is actually the only scene in the movie that made me laugh.
Sinbad calms them down and explains he's not there to kidnap them or anything, and that for freeing him they will be granted three wishes.
The boy is skeptical and asks for something stupid -seems like it was something that flew...like a magic carpet or flying skateboard.
The genie grants the wish and the kids are amazed. I think the little girl asks for her mother back, and Sinbad tries to show his tender emotional side by explaining with a tear in his eye that "I'm afraid I can't do that"
After the genie goes back in the bottle, the kids talk it over and make a promise to each other to save the other wishes for something really important, but they agree that one of the wishes should be to find a new wife for their dad , that they will like too.
The little girl is really attached to her doll and breaks it by accident while the boys are out of sight in the yard or something and she uses a wish to fix the doll.
The girls' brother comes to her later with an idea for their second wish and the girl has to admit she already used it.So, with one wish left, the climax of the movie takes place at a pool party where a lot of slapstick comedy takes place and gimmicky film techniques like speeding up the film speed are used to make things look more cartoon like and funny - but it ended up just looking dumb to me.
One piece of residue discovered on the Mandela Effect subreddit is a reference to the movie Shazaam on the Michigan State News website. 
Apart from this, several posters of the movie have been made by people who are affected by this Mandela Effect. These posters, while not authentic, have been created with the help of memories shared by many people.
Potential ExplanationsThe most common explanation for this Mandela Effect is that people are simply confusing the movie for another extremely similar movie released around the same time, Kazaam. This movie stars Shaquille O'Neal, and is about a genie - similar to the description of the Shazaam movie. All That, in which he plays the role of a genie.
A theory posted on Reddit states that people may also be remembering Sinbad's fashion in the 1990's, which was similar to a genie with baggy and colorful clothing. 
Lastly, Sinbad himself has claimed that the confusion comes from his role in a "movie night"-style hosting role, where he appeared as a genie and presented his own movies. 
- Sinbad Genie, Reddit|https://www.reddit.com/r/MandelaEffect/comments/4v3js5/sinbad_genie_theory/d5vmbgt/
- Michigan State News|http://wayback.archive-it.org/2443/200012091058/http://www.statenews.com/editionsfall98/110498/op_col2.html
- Is this a real Shazaam movie poster?|https://www.reddit.com/r/MandelaEffect/comments/5ldkek/is_this_a_real_shazaam_movie_poster_or_am_i_that/
- Opening To My 1997 VHS of Sinbad's First Kid|https://youtu.be/sWCg8Y5t_P0?t=1m49s
- Shazaam Theories, Reddit|https://www.reddit.com/r/MandelaEffect/comments/5li90m/shazaam_theories/
- Possible Explanations of why People Remember a Sinbad Genie Movie|https://www.reddit.com/r/MandelaEffect/comments/5uoulg/possible_explanations_of_why_people_remember_a/
- Sinbad Twitter|https://twitter.com/sinbadbad/status/783083506662383616/