Yeah Warnermedia (the company that includes Warner Bros) own a lot of stuff. For reference,
this Wikipedia article has a list of assets Warnermedia owns.
For the three mentioned characters, Stripe is from Gremlins (a WB movie). Gilligan's Island was a result of Turner acquiring MGM and then selling it, but keeping some of its assets (including the pre-1986 MGM library, the Popeye Cartoons, distribution rights to RKO Radio Pictures library, and, humorously, Warner's own pre-1950 library (including cartoons)). Robotron is because Williams (original developers also famous for games such as Defender) transferred rights to their Video Game franchises to Midway in 1996 (that same year Midway purchased Atari Games (not the actual Atari but a spin off corporation) which includes games such as Paperboy and Gauntlet). Warner Bros acquired the Midway library in 2009 and has used it in various game compilations and Lego Dimensions.
And with the merger with Discovery happening in the future, that adds a lot more potential properties (although I think the game will be out before the merger happens).