They really pushed the 'Hello Larry'/'Strokes crossovers, with a pair of two-part stories tht aited on both series, and one Thanksgiving show on 'Strokes'.
On a different site the other day, a discussion of crossovers mentioned one with 'Fantasy Island' and 'The Love Boat', in 1980, in which two guests appeared on each show. First, a half-hour 'Island', with one guest, a terminally ill girl who is cured. At the end of the episode, the family said they were going on a cruise...aboard the Pacific Princess...and they had a storyline in the 90-minute 'Love Boat' episode that followed.
A different storyline in that episode starred Loni Anderson, in the unusual role of a woman with a miserable life before the cruise, who was even MORE miserable near the end of the episode. Then, Julie McCoy mentions the 'resort on Fantasy Island', and they make arrangement for Anderson's character to be picked up from the ship by a motor boat that takes her to the island, where, in the second 'Fantasy Island' episode, Roarke solves her problem, along with whatever else was going on that week.
The 'Love Boat' also appeared in an episode of 'Charlie's Angels', where the ladies went undercover, while pursuing a jewel thief who had boarded the ship to get away from them.